Make ringtones in iTunes

Recent (2011) versions of iTunes allow easy conversion of audio files to ringtones for the iPhone.

1. Make sure your import options make MP4 audio files, the format used for iPhone ringtones.
   1. Open iTunes.
   2. Open Preferences.
   3. In the General tab select Import Settings.
   4. Set Import Using...AAC Encoder.
   5. Close Preferences window.
2. Pick a song
3. Set iTunes to repeat a single song.
   1. Select a song.
   2. Click on the repeat symbol until it is highlighted with the number 1.
4. Shorten the song
   1. Right-click or control-click on a song and select Get Info.
   2. Go to the Options tab.
   3. Check the boxes next to Start Time and Stop Time.
   4. Input the time in minutes:seconds for a start and stop that are less than or equal to 30 seconds apart. I often repeat the first 4, 8, or 16 measures which contain some interesting "hook." Press pause and play every time you change the times, so that iTunes uses your new settings. Try to make the seam between the end time and the start time less noticeable by matching the rhythm over the transition.
   5. Close the info box.
5. Export the song using the Advanced Menu...Create AAC Version.
6. Change the exported file to a ringtone.
   1. Right click on the shortened version and select Show In Finder.
   2. Change the name from filename.m4a to filename.m4r
7. Remove the original shortened file from iTunes by selecting it then pressing command-delete or command-backspace.
8. Import the m4r file to iTunes by double-clicking it in Finder. iTunes will keep it in the Tones window.

Whether you sync all ringtones or just selected ones to your iPhone is up to you. It is a setting in the Tones pane of your device window.