[De4dpOol]

pawn Код:

public OnPlayerRequestClass(....)
{
    SpawnPlayer(playerid);//To spawn the player
    ShowCustomClassSelection(playerid);//Create a stock function to set up the custom class selection.
    return 1;
}

Create a stock function to send the player to class selection at OnPlayerRequestClass.
Edit: I added Spawn Player as it will need to spawn him first.