If you already have songs you want to make a ringtone, this
http://osxdaily.com/2010/09/04/make-free-iphone-ringtones-in-itunes-10/ showed how:
Sep 4, 2010 - 193 Comments
Apple took the functionality to buy a ringtone out of iTunes 10 for some reason, but that doesn’t mean you can’t have custom ringtones. You can make your own free iPhone ringtones directly within iTunes 10, this is the best way to go since you don’t have to get any additional software or pay for a service to create the files. Don’t download or pay for one of the iPhone ringtone maker apps, just launch iTunes and follow this guide, it’s easy to do and totally free.
Make an iPhone ringtone in iTunes 10
If you’ve made an iPhone ringtone before the process will be familiar to you. This will work the same on both Mac and Windows versions of iTunes 10:
Launch iTunes 10
Find and select the song you want to make a ringtone out of in iTunes 10
Right-click on the song name and select ‘Get Info’, then click on the Options tab
Select the playback period of the song that you want to ringtone to be, make sure it’s 30 seconds
Now click "OK” and then right click on the song again, and select "Create AAC version” to create a new version of the song with the 30 second interval you specified
Locate this newly created 30 second clip in iTunes (at the top of the playlist if you search by ‘date added’ and right click on the file and then select "Show in Finder”
Now in the Finder (or Windows explorer, the process is the same for Windows iTunes 10), rename the file extension from .m4a to .m4r
Accept the file extension change to .m4r
Now back in iTunes remove the file from the playlist (do NOT move to Trash, select ‘keep file’) and then re-import the file into iTunes 10 by double clicking the .m4r file within the Finder or Windows
The file will now be added back into iTunes as a ringtone and you can do what you want with it
Sync it with your iPhone and assign to contacts as usual with custom iPhone ringtones
If you used iTunes 9 to make custom iPhone ringtones the process is very similar.
Enjoy your free iPhone ringtones!