The machine nearest the door is the best to play on. Don't play on little machines that are in gas stations and places like that. Play through your money once only. Play the maximum amount of coins always. Machines with more than one payout line should be avoided.
Luck is the only thing to do with anything.
The RNG proves that. The loosest slots are placed in high traffic areas. The more paying symbols on a machine, the more of a loser it is. Splitting three against a dealer's five is a good idea. Split deuces against a dealer's four.