You can create ringtones in iTunes using songs purchased from the iTunes Store (not available in all countries). Your iTunes Store account will be charged for each ringtone.

Create a ringtone:

  1. In iTunes on your computer, choose iTunes > Preferences and make sure Ringtones is selected (in the General pane).
  2. Make sure you are connected to the Internet.
  3. To identify the purchases you can use to create ringtones, choose View > View Options and then select Ringtone. (If a message appears, click Check Songs.)

    To identify eligible purchases later, choose iTunes > Check for Updates.

  4. Select the song you want to use and then choose Store > Create Ringtone.
  5. Adjust the highlighted area at the bottom of the iTunes window to choose up to 30 seconds of the song.
  6. To make the ringtone fade in or out, select either or both “fade” checkboxes.
  7. To change the delay before the ringtone plays again, choose an interval from the Looping pop-up menu.
  8. To listen to the ringtone, click Preview.
  9. Click Buy.

IMPORTANT: After you click Buy, you can change the ringtone’s name and other information, but you can’t select a different portion of the song.

You can sync ringtones created with iTunes with any iPhone you own, and play them on up to five authorized computers. After you sync your iPhone, you can assign the ringtone to one or more contacts.

You can also create custom ringtones in Garage Band. See Garage Band Help for more information.

http://www.apple.com/iphone/tips/