Sell sealed envelops with coupons for instant winners. This is a great way to mingle with people during an event. Get a large number of envelopes and fill each one either with a winning coupon or a 'Better luck next time' note. Make sure 1 in 4 is a winner. Mix all the envelopes well. Punch a hole on the corner of the sealed envelope and hang all yoru envelopes on a large ring - or two. Volunteers carry the rings and watch their collection decrease as they work the crowd to sell envelopes.