How make the server do something when the client joins the game?

[yhflab]

I am creating a default preference.

I need these things to be initialized when the client joins the game.

How can i do that?

and how to let a player's works are not available? I mean, whatever he does, these things won't happen.

Another big big question:

If a player is already done some commands, how can i know this is the second time?

Thank You!! I love ya!

[yhflab]

Thanks a lot man, my English is so horrible im sry about that anyway, thank U very much