Session variables

I'm new to PHP and need a bit of help. I'm not sure if this is the best of way of doing this but I have two pages: 1. newmemberlogin.php - this is basically a form asking for information about the user and saves it in sessions. 2. login.php - this logs the person in and greets them with their first and last name. What i'm stumped on is the following in pseudo-code: if (session exists) { print "$firstname $lastname" //comes from session saved from newmemberlogin.php } else { query = mysql_query (select * from clients where username=username(from form) print $firstname $lastname //prints name, data from database save data from database into session } I have no idea how to query data and save it into a session. Thanks, Mike