I WOULD NOT RECCOMEND U WANTING TO CRACK YOUR JAW. I've been doin this since i was a kid. I'm trying to stop. But here's how i do it; and i can only do the right side. I make a fist and make the index finger stick out a little more to make contact with the jaw bone a little down from the ear on the side of your face and tense my jaw muscle and then untense it and then hit it with the index finger. It sometimes takes a while. Since my finger has been getting soar from hitting it i use a small hammer. I know this sounds weird..but it works for me. Happy cracking!!
R