1.Go to iTunes and select a song you want to make ringtone of.
2.Right click on the song and select „Get Info“.
3.Select tab „Options“ and find „Start Time“ and „Stop Time“ check boxes.
4.Check both boxes and input the time you want the ringtone to start and stop. Be aware, that the ringer has to be 30 seconds or less. Click OK.
5.Right click on your new ringtone (shortened version of the song) and select „Convert Selection to AAC“. This means your song will be encoded to AAC format which is needed to play on your iPhone.
6.After the song is encoded, find it and drag the song to your desktop.
7.Go back to your iTunes library and delete the song from your playlist. This won’t mean the version on your desktop will be deleted.
8.Right click on the song on your desktop, select „Get Info“ and change the extension from .m4a to .m4r.
9.After changing the extension, double click on the file to add it to your iTunes library under the ringtones selection.
10.Sync your phone with iTunes and you’re done!