How to Create ringtones for your iPhone with iTunes
This video tutorial features Lisa Bettany, describing how to create your own ringtones on your iPhone. First you need to modify your import settings to aac encoder, then make sure you list high quality. When this is done hit "ctrl I" to set the time frame of your song. Right click this file and hit create aac version. From here you must delete the original song that you took the clip from. You must then change the extension of the file to .m4r. From here you just have to sync your iPod to iTunes. From there just add the ringtone and it will be added to your phone.