You decided how many marbles each person was going to put in and they were placed, more or less, in the center of the circle. The circle itself varied in size mainly depending on the skill level of the players. Your hand was placed on the ground just at, but not over, the edge of the circle and you would shoot at the marbles inside of the ring trying to knock them out of the ring. If you managed to get one out and your 'shooter' stayed in, you could shoot again. Your next shot was from the spot that your marble stopped at, much like pool. When you failed to get a marble out of the ring the next player shoots. There were a couple of variables on shooting style. Some people would 'pinch' the marble between the thumb and upper part of the forefinger, but most 'pushed' out the marble from a curled index finger with their thumbnail portion of their thumb. (Much like flipping a coin.)
Also, marbles that were clear were called 'crystals' and they were our most prized. Sometimes people would put in marbles but would play for their 'shooters.'