On the rare occasion I want to make a song clip for a ringtone, I use Nero Wave Edit.

Mostly I have some website saved in my favorites on my phone's browser that has a whole ton of free ringtones already clipped down to the right length.

Even more mostly I have my phone on vibrate so that unless it's directly on me or on a desk/table right next to me I don't know that it's ringing and I am forced to maybe remember to call people back if they leave me a voicemail and I ever get around to listening to it.