how to tell when people first joins the server

Title says it all.

Thanks if you can help me.

You could save their id in a file or in a mySQL database and check for it when they join.

If you use ulx for an admin mod you could use this. http://forums.ulyssesmod.net/index.php?topic=6036.0. It prints a message in chat when someone joins. When you join, it will be the first thing you see in chat.