While Apple still allows you to purchase alert tones directly from the iTunes Store, many users may already have their own sound effects or songs that they already own that they’d like to use as ringtones or alert tones. Unfortunately, while iTunes doesn’t provide any way to do this directly, if you already have a short sound file in the AAC format you can actually import it straight into the “Tones” section in iTunes simply by renaming the file, changing the extension from M4A to M4R before importing it.

If your file is longer than about 30 seconds and/or in a format other than AAC, however, you’ll need to take some additional steps. See this week’s Ask iLounge article Setting up a ringtone in iTunes for more information.