Creating your own iPhone ringtones using Apple's iTunes software is easy, but it can take some… More

Instructions
Things You'll Need:

* iTunes
* Mac or Windows computer
* Non-DRM song (i.e., one not bought from the iTunes Store)

#1 Open iTunes.
#2 Find the song that you want to make into a ringtone.
#3 Listen to the song and find the part of it you want to use. The chorus may be a good place to start.
#4 Write down the start and stop times of the clip.
#5 Right-click the song and select "Get Info."
#6 Click the "Options" tab.
#7 Type in the start time of your ringtone in the text box next to "Start Time" in the minutes:seconds (i.e., 2:01) format.
#8

#9 Click "OK."
#10 Right-click your song again and select "Convert Selection to AAC." Wait for iTunes to convert your song. It will create a duplicate version.
#11 Right-click the ringtone and select "Delete."
#12 Click on the "Keep Files" button.
#13 Find the file. It's usually in your User folder under "Music > iTunes > iTunes Music" and under the band's name. It will have an extension of m4a.
#14 Replace the m4a extension of your ringtone with m4r. You can either double-click slowly to rename your file, or right-click and select "Get Info" on a Mac or "Rename" on a Windows PC.
#15 Replace the m4a extension of your ringtone with m4r. You can either double-click slowly to rename your file, or right-click and select "Get Info" on a Mac or "Rename" on a Windows PC.
#16 Click "Use .m4r" or the PC equivalent when the system warns you that the change may affect the use of your file.
#17 Double-click the ringtone file. ITunes will automatically add it to your ringtones folder in your iTunes Music Library.
#18 Connect your iPhone and sync your ringtones.

*Works with latest Itunes 10