Up to six. You only need one, but you better be confident in your playing ability if you use less than two.

[He is not entirely confident in his playing ability, so he picks the red pin with the skull on it, one with flames, a couple with chains, and the 'M' and 'O' pins.]

Okay...so you pick a pin to start out, and put it at the edge of the uhh-- [He forgot to designate a playing field, didn't he? He grabs a marker from his pocket and draw a large circle on the table, then sets one of his pins on the line.] --circle. And then you just...flick it at your opponent's pin and try to knock it out of the circle. If that pin gets knocked out, you use another, until you run out of pins.