With a few clicks you can turn your favourite song into a ringtone for your iPhone:
1. Select a song in iTunes (if the file format is MP3 convert it to ACC by right-clicking on the selected song and choosing “Create AAC Version”).
2. Select the created AAC Version and press Cmd + i
3. Go to “Options” and check “Start Time” and “Stop Time”. Set the time code to the part of the song you want (30 seconds max).
4. Drag the song from the iTunes Library to your desktop and change the ending to .m4r
5. Now drag the renamed file back into iTunes and it will show up under “Ringtones” ready for the next iPhone sync.