I sometimes put a couple of quid on the lottery if I fancy it, but it's just a spur of the moment thing.
The only other time I gamble is when I KNOW I will win. I used to work in a bookies, and we'd have a woman come in every so often to make MASSIVE bets on dogs, combination tricasts on the whole. She'd make about 6 of these bets, and at least 4 would come in, if not 6, and they would PAY.
So I used to duck out when she came in, whack the bets down on the next bookies round the corner and make a mint myself!