Well, I've been on a few auto extrication jobs.

First of all, before you bust out a window to get a person out of a car - try the door, ofetn enough, it will open. If they hit hard enough that the doors are jammed, the windows are often blown out anyway.

As far as seat-belt cutters and the like, I just use a utility knife (sheetrock knife) and a spring-loaded center punch. Keep the dull side of the blade toward the victim. Remember to cut both the lap and shoulder belt. To punch a window, put your spring loaded punch down in a corner of the window, hold it in one hand and hold the other hand around the punch. Ideally, you'll want to be wearing gloves, if not you WILL get a cut as the glass blows out. Also bear in mind that this technique DOES NOT work on Windsheilds, Rear Windows, and on the side windows of some late model cars. If the airbags deployed, bear in mind that they might not have ALL deployed and you (and the patient) are at some risk of injury. While it's not always possible, try reaching in and turing off the ignition, which will de-energize the airbags (but not immediately). If this is not possible, try cutting the NEGATIVE (black) battery lead. If that's not possible, you just gotta go for it.

Hope that helps.