2 Methods to Get iPhone Ringtone from iTunes
There are normally 2 ways you can get iPhone ringtones from your favorite music since the release of iTunes 8.
The first one is buying directly from iTunes store. Although this is quite convenient and you can easily find those made from your favorite music, the problem is the 30 seconds you bought may be not as special or whatever as you expected.
May be just because of this, then here comes the second way. iTunes actually allows you to customize your iPhone ringtones from your favorite music. But keep in mind that all the music must have been purchased by you. It works quite easy too.
Step1. Fire up the iTunes and choose the song you'd like to turn into a ringtone
Step2. Right click on the song and select "Get Info".
Step3. Select 'create Ringtone' to begin to create
After you finish making a ringtone, pay another $0.99, you can now enjoy your unique iPhone ringtone.

Although these two methods are convenient, apparently, they all come with fees, even with the song you've bought. In addition, some music (including those free ones) in iTunes cannot be used to make ringtones, let alone making from ripped CDs, Video clips or Movies.