Couldn't be easier!

Just create a playlist in iTunes (using the "+" button at the bottom left of the main window) and drag the songs you want on the CD into the playlist. While viewing the playlist, you can also drag them around to reorder them if you like. Remember that a standard audio CD stores only 74 or 80 minutes of music, depending on the blanks you use. When you're ready to go, hit the "Burn CD" button at the top right. iTunes will ask you to insert a blank CD if you haven't already done so, and hit "burn CD" again to start.

Mark (clueful in New York)
2.8.5/10.2.3/iMac 800 (and a few others)