SetPlayerCheckpoint(playerid, Float:x, Float:y, Float:z, Float:size);

Playerid - This is the ID for who the checkpoint will be
Float:x – The X position
Float:y – The Y position
Float:z – The Z position
Float:size – This will be the size of the checkpoint (normal checkpoint is around the 2-3)

SetPlayerRaceCheckpoint(playerid, type, Float:x, Float:y, Float:z, Float:nextx, Float:nexty, Float:nextz, Float:size)

Playerid – This is the ID for who the checkpoint will be
Type – You got 4 different types. 0 = normal checkpoint (arrow inside), 1 = finish checkpoint, 2 = checkpoint without an arrow inside, 3 = checkpoint in the air (circle), 4 = finish checkpoin for in the air.
Float:x – The X position
Float:y –  The Y position
Float:z – The Z position
Float:nextx – This is the X position, for the next checkpoint. This is just for the arrow, so it knows which direction it needs to point at.
Float:nexty – This is the Y position, for the next checkpoint. This is just for the arrow, so it knows which direction it needs to point at.
Float:nextz – This is the Z position, for the next checkpoint. This is just for the arrow, so it knows which direction it needs to point at.
Float:size – This willb e the size of the checkpoint. Also, a normal size is around the 2-3.

DisablePlayerCheckpoint(playerid);

DisablePlayerRaceCheckpoint(playerid);

new Ccp[MAX_PLAYERS];  // This creates a variable, which we will use later

COMMAND:work(playerid, cmdtext)
{
    Ccp[playerid] = 1; // This will change the variable, so we can use it later on with OnPlayerEnterCheckpoint
    SetPlayerCheckpoint(playerid, -269.1287,2610.6057,63.2069, 3.0); // This creates a checkpoint at the coцrdinates: "-269.1287,2610.6057,63.2069"
    SendClientMessage(playerid, 0xFFFFFFFF, "You started your first mission. Please follow the checkpoints");
    return 1;
}

public OnPlayerEnterCheckpoint(playerid)
{
    if(Ccp[playerid] == 1) // This checks if our variable equals to 1, if so: it continues
    {
        DisablePlayerCheckpoint(playerid); // This makes sure that there will be a new checkpoint
        Ccp[playerid] = 2; // Changes the variable, so we can use it later again with OnPlayerEnterCheckpoint
        SetPlayerCheckpoint(playerid, -1051.4005,-655.8729,31.7361, 3.0); // Creates a new checkpoint at a different position
        SendClientMessage(playerid, 0xFFFFFFFF, "You loaded your goods, go to the next checkpoint to continue.");
        return 1;
    }
    return 1;
}

public OnPlayerEnterCheckpoint(playerid)
{
    if(Ccp[playerid] == 1) // This checks if our variable equals to 1, if so: it continues
    {
        DisablePlayerCheckpoint(playerid); // This makes sure that there will be a new checkpoint
        Ccp[playerid] = 2; // Changes the variable, so we can use it later again with OnPlayerEnterCheckpoint
        SetPlayerCheckpoint(playerid, -1051.4005,-655.8729,31.7361, 3.0); // Creates a new checkpoint at a different position
        SendClientMessage(playerid, 0xFFFFFFFF, "You loaded your goods, go to the next checkpoint to continue.");
        return 1;
    }
    if(Ccp[playerid] == 2) // This checks if our variable equals to 2, if so: it continues
    {
        new reward, string[128]; // This will create 2 new variables, a reward: so we can print the reward later on. string[128]: This creates a variable, with the size "128", we'll use this one to make a message.
        DisablePlayerCheckpoint(playerid); // This will destroy the checkpoint, so you only get your reward once
        Ccp[playerid] = 0; // This resets the variable, so if you enter a checkpoint right now, nothing will happen
        reward = GivePlayerMoney(playerid, GetPlayerMoney(playerid) + random(5000) + 1000); 
        /* 
        With this it will change the money. 
        What does the random function: This will get a random number, between 0 - 5000. After he gets a random number, he will add 1000 to it, and then add that amount of cash to your current amount
        */
        format(string, sizeof(string), "You entered the last checkpoint. Reward: $%i", reward); 
        /*
        If the reward is 3676 (example), this will print: You entered the last checkpoint. Reward: $3676
        What is the %i? The %i stands for "Integer", also known as a number. If the %i was %s, it only would have print letters, because %s = string
        */
        SendClientMessage(playerid, 0xFFFFFFFF, string); // This sends the string to the player
    }
    return 1;
}

ShowPlayerDialog(playerid, dialogid, style, caption[], info[], button1[], button2[])

Playerid - This is the ID for who the dialog will be
Dialogid - The id for the dialog. This is so we can give it a response (Max ID = 32767)
Style - There are 3 different styles: DIALOG_STYLE_MSGBOX, DIALOG_STYLE_INPUT, DIALOG_STYLE_LIST. MSGBOX = just a messagebox, INPUT = inputbox, LIST = dialog with listitems
Caption[] - This will be the "title" of the dialog. Max = 64 characters
Info[] - This will be the text (info), with \n you can make a new line (Used to make listitems for LIST)
Button1[] - This will be the text of the first button
Button2[] - This will be the text on the second button

COMMAND:work(playerid, cmdtext)
{
    ShowPlayerDialog(playerid, 50, DIALOG_STYLE_LIST, "Choose any of those locations", "From --- to --- /*(listitem 0)*/ \nFrom --- to --- /*(listitem 1)*/ \nFrom --- to ---/*(listitem 2)*/", "Ok", "Cancel"); 
    /*
    As you can see, im using "\n" to make a new line. In a messagebox it is just a new line, but with DIALOG_STYLE_LIST, it is a new listitem. 
    Please NOTE: Anything always start couting from 0, not from 1. 
    You can change the dialogid to anything, and an usefull thing to do, is to give the dialog an name.
    Example: 
    #define MISSIONDIALOG   50
    ShowPlayerDialog(playerid, MISSIONDIALOG, DIALOG_STYLE_LIST, "Choose any of those locations", "From --- to ---  \nFrom --- to ---  \nFrom --- to ---", "Ok", "Cancel"); 
    So if you need to change the dialogs, because you're already using the dialogid, you just need to change 1 number, instead of the whole dialogid's
    */
    return 1;
}

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    if(dialogid == 50 || dialogid == MISSIONDIALOG) // This checks if the dialog equals to 50, OR ( || = or , && = and ) MISSIONDIALOG. Just change it to what ever you use. You can use a switch aswell, but i just prefer just to see the whole line
    {
        if(!response) return 0; // If you press the second button (cancel), the dialog dissapears and nothing happens
        if(resposne) // if there is a response (first button( ok )) it continues
        {
            if(listitem == 0) // If you choose the first listitem, this happens
            {
                Ccp[playerid] = 1; // This will change the variable, so we can use it later on with OnPlayerEnterCheckpoint
                SetPlayerCheckpoint(playerid, -269.1287,2610.6057,63.2069, 3.0); // This creates a checkpoint at the coцrdinates: "-269.1287,2610.6057,63.2069"
                SendClientMessage(playerid, 0xFFFFFFFF, "You started your first mission. Please follow the checkpoints");
                return 1;
            }
            if(listitem == 1) // If you choose the second listitem
            {
                Ccp[playerid] = 3; // Why do we make this one 3, and not just 1? That is because 1 is already in use. If you look at your current OnPlayerEnterCheckpoint, you see that there already is a "if(Ccp[playerid] == 1)"
                SetPlayerCheckpoint(playerid, -1051.4005,-655.8729,31.7361, 3.0); // This creates a checkpoint at the coцrdinates: "-1051.4005,-655.8729,31.7361"
                SendClientMessage(playerid, 0xFFFFFFFF, "You started your first mission. Please follow the checkpoints");
                return 1;           
            }
            if(listitem == 2) // If you choose the third listitem
            {
                Ccp[playerid] = 5; // Same for this, 1, 2, 3 and 4 are already in use, so thats why we use 5
                SetPlayerCheckpoint(playerid, -2286.7529,2282.9390,5.9015, 3.0); // This creates a checkpoint at the coцrdinates: "-2286.7529,2282.9390,5.9015"
                SendClientMessage(playerid, 0xFFFFFFFF, "You started your first mission. Please follow the checkpoints");
                return 1;           
            }
        }
    }
    return 1/0 // If you're using this in your GM, then return to 1. If you're using a FS, return to 0 PLEASE NOTE: Take a good look at this, if you're returning to 1 in a FS, it will NOT work
}

public OnPlayerEnterCheckpoint(playerid)
{
    if(Ccp[playerid] == 1) // This checks if our variable equals to 1, if so: it continues
    {
        DisablePlayerCheckpoint(playerid); // This makes sure that there will be a new checkpoint
        Ccp[playerid] = 2; // Changes the variable, so we can use it later again with OnPlayerEnterCheckpoint
        SetPlayerCheckpoint(playerid, -1051.4005,-655.8729,31.7361, 3.0); // Creates a new checkpoint at a different position
        SendClientMessage(playerid, 0xFFFFFFFF, "You loaded your goods, go to the next checkpoint to continue.");
        return 1;
    }
    if(Ccp[playerid] == 2) // This checks if our variable equals to 2, if so: it continues
    {
        new reward, string[128]; // This will create 2 new variables, a reward: so we can print the reward later on. string[128]: This creates a variable, with the size "128", we'll use this one to make a message.
        DisablePlayerCheckpoint(playerid); // This will destroy the checkpoint, so you only get your reward once
        Ccp[playerid] = 0; // This resets the variable, so if you enter a checkpoint right now, nothing will happen
        reward = GivePlayerMoney(playerid, GetPlayerMoney(playerid) + random(5000) + 1000); 
        /* 
        With this it will change the money. 
        What does the random function: This will get a random number, between 0 - 5000. After he gets a random number, he will add 1000 to it, and then add that amount of cash to your current amount
        */
        format(string, sizeof(string), "You entered the last checkpoint. Reward: $%i", reward); 
        /*
        If the reward is 3676 (example), this will print: You entered the last checkpoint. Reward: $3676
        What is the %i? The %i stands for "Integer", also known as a number. If the %i was %s, it only would have print letters, because %s = string
        */
        SendClientMessage(playerid, 0xFFFFFFFF, string); // This sends the string to the player
        return 1;
    }
    if(Ccp[playerid] == 3) // This checks if our variable equals to 3, if so: it continues
    {
        // This is the same as "if(Ccp[playerid] == 1)", didn't understand something from this? Please look back
        DisablePlayerCheckpoint(playerid); 
        Ccp[playerid] = 4; 
        SetPlayerCheckpoint(playerid, 2791.8650,1231.7740,10.7663, 3.0); 
        SendClientMessage(playerid, 0xFFFFFFFF, "You loaded your goods, go to the next checkpoint to continue.");
        return 1;
    }
    if(Ccp[playerid] == 4) // This checks if our variable equals to 4, if so: it continues
    {
        // This is all the same as with "if(Ccp[playerid] == 2)", so if you still didn't understand anything from it, please, look back at the Ccp[playerid] == 2
        new reward, string[128]; 
        DisablePlayerCheckpoint(playerid); 
        Ccp[playerid] = 0; 
        reward = GivePlayerMoney(playerid, GetPlayerMoney(playerid) + random(5000) + 1000); 
        format(string, sizeof(string), "You entered the last checkpoint. Reward: $%i", reward); 
        SendClientMessage(playerid, 0xFFFFFFFF, string);
        return 1;
    }
    if(Ccp[playerid] == 5) // This checks if our variable equals to 5, if so: it continues
    {
        // This is the same as "if(Ccp[playerid] == 1 || Ccp[playeird] == 3)", didn't understand something from this? Please look back
        DisablePlayerCheckpoint(playerid); 
        Ccp[playerid] = 6; 
        SetPlayerCheckpoint(playerid, -1573.3285,-2730.4099,49.2886, 3.0); 
        SendClientMessage(playerid, 0xFFFFFFFF, "You loaded your goods, go to the next checkpoint to continue.");
        return 1;
    }
    if(Ccp[playerid] == 6) // This checks if our variable equals to 6, if so: it continues
    {
        // This is all the same as with "if(Ccp[playerid] == 2 || Ccp[playerid] == 4)", so if you still didn't understand anything from it, please, look back at the Ccp[playerid] == 2 || Ccp[playerid] == 4
        new reward, string[128]; 
        DisablePlayerCheckpoint(playerid); 
        Ccp[playerid] = 0; 
        reward = GivePlayerMoney(playerid, GetPlayerMoney(playerid) + random(5000) + 1000); 
        format(string, sizeof(string), "You entered the last checkpoint. Reward: $%i", reward); 
        SendClientMessage(playerid, 0xFFFFFFFF, string);
        return 1;
    }
    return 1;
}

CreateDynamicCP(Float:x, Float:y, Float:z, Float:size, worldid = -1, interiorid = -1, playerid = -1, Float:distance = 100.0);

Those are the new things that have been added, i’ll explain those, and the rest you would know if you read the tutorial above

Worldid – This is the VirtualWorld where the checkpoint will be. If this one is -1, then it will be shown in EVERY VirtualWorld
InteriorID – This is the Interior where the checkpoint will be. If this one is -1, then it will be shown in EVERY interior
Playerid – Again, this will be the player for who the checkpoint will be, most likely is to leave this at -1 so it is for everyone.
Float:distance – This will be the distance from where you will see the checkpoint. If it’s 100 (recommed), then you will see the checkpoint if youre 100 meter (not sure if it’s in meters) away from it. 
DestroyDynamicCP(checkpointid);

CreateDynamicRaceCP(type, Float:x, Float:y, Float:z, Float:nextx, Float:nexty, Float:nextz, Float:size, worldid = -1, interiorid = -1, playerid = -1, Float:distance = 100.0);
DestroyDynamicRaceCP(checkpointid);

new Checkpoint[2]; 
/*
Put this above your script out of any callback. This will create a variable that you will use to create the checkpoints. 
Also, change the number between the [ ] to the amount of checkpoints you have. But don't forget to add 1 extra to it! Otherwise you get this error:
error 032: array index out of bounds (variable "Checkpoint")
*/

public OnPlayerSpawn(playerid)
{   
    Checkpoint[0] = CreateDynamicCP(-2112.7422,-753.4459,32.1719, 4, -1, -1, -1, 100); // Creates a checkpoint at -2112.7422,-753.4459,32.1719 with a range of 4, in any virtualworld, interior and for every player
    Checkpoint[1] = CreateDynamicCP(-2112.9177,-760.9539,32.1719, 4, 5, -1, -1, 100); // Creates a checkpoint at -2112.9177,-760.9539,32.1719 with a range of 4, in virtualworld 5, any interior, and for every player
    return 1;
}

public OnPlayerEnterDynamicCP(playerid, checkpointid)
public OnPlayerEnterDynamicRaceCP(playerid, checkpointid)
playerid - This is the action what the player gets when he enters the CP
checkpointid - This is the checkpoint id, this will be the variable we used above

public OnPlayerEnterDynamicCP(playeird, checkpointid)
{
    if(checkpointid == Checkpoint[0]) // Checks if the checkpointid equals to Checkpoint[0]
    {   
        SendClientMessage(playerid, 0xFFFFFFFF, "This is \"Checkpoint[0]\"");
        /*
        NOTE: The " \ " is needed before the ", otherwise it will give you an error!
        You wont see the " \ " though, so dont worry about that
        */
        GivePlayerMoney(playerid, + 100);
    }
    if(checkpointid == Checkpoint[1]) // Checks if the checkpointid equals to Checkpoint[1]
    {
        SendClientMessage(playerid, 0xFFFFFFFF, "This is \"Checkpoint[1]\"");
        GivePlayerMoney(playerid, + 200);
    }
    return 1;
}