1- from itune select any song you want it to be a ringtone.
2- right click on it select GET INFO.
3- select option tap
4- input the desire start time and stop time until 30sc or 40 as max.
5- go back to the song and right click on it to convert it to ACC format
6- this would give you a 30sc portion. Drag it to the desktop and modify the extension to .m4r
7- put it back in the Ringtone library in the iTune then sync with your iPhone
8- IT's FREE