You will need GarageBand and iPhone firmware 1.1.2 on your iPhone, also, of course, a version of iTunes that supports official ringtones. Even if you havent bought GarageBand, you get a demo version with your Mac, so use that for now... This is very easy just make sure you have the latest version (or you wint have the right feature for iPhone ringtones) then open it up and drag the file you want to use as a ringtone in to your GarageBand then set up a cycle region that covers the area you wish to use in the GarageBand song. Note: This area must be 40 seconds or less (the phone probably wont stay ringing for that long anyway). Then all you have to so is click "Share" then "Send Ringtone to iTunes" and thats it, just sync that ringtone to your iPhone in iTunes and you have your ringtone on there!