ShowPlayerDialog(playerid,dialogid,DIALOG_STYLE_LIST,"MyDialog","1. Line\r\n2. Line\r\n3. Line","Option 1", "Option 2");
public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
      switch(dialogid) // Lookup the dialogid
      {
          case 1:
          {
              if(!response)
              {
                  SendClientMessage(playerid, 0xFF0000FF, "You press Option 2.");
                  return 1; // We processed it
              }
     
              switch(listitem) // This is far more efficient than using an if-elseif-else structure
              {
                  case 0: // Listitems start with 0, not 1
                  {
                      // What should happen when they click on the first item?
                  }
                  case 1:
                  {
                      // And the second item?
                  }
                  case 2:
                  {
                      // We can keep going on here  
                  }
                    
                  // Add the rest of your listitems for dialog 1 here
     
              }
     
          }
          // Add the rest of your dialogs here
     
      }
      return 1;
}