The odds on any casino game, including slots are always in favor of the casino. That being said, there are some guidelines to follow if you want to maximize profits and minimize losses. Never play with more money than you can afford to lose, and play with caution. Penny slots, with their low cost per game are a great option for those without a lot of money to spend, and the payoffs can be excellent if follow a few guidelines.
Take only as much money as you're willing to lose to the casino. Leave your credit and debit cards at home. It's easy to get on a winning or losing streak and think "just one more game". Gambling when you're desperate or even euphoric can cause you to lose focus and spend much more than you planned.
Choose machines with the highest payout percentages and bonus opportunities. By picking the highest paying machines, you are essentially maximizing your profits before you spend a penny. Bonus opportunities (usually prompted by getting a particular picture a certain number of times anywhere on the screen) can significantly boost your winnings. Winning a bonus can mean you get to play a short sub-game, or you might just be rewarded outright with extra winnings.
Play the maximum number of lines available. If you are betting one penny per line, the amount you are wagering for each play is equal to the number of lines you play. For example, betting one penny per line and playing one line will cost you one penny per spin, but playing 20 lines will cost you 20 cents per spin. You will up the odds per spin while betting the same amount per line. This does result in fewer spins, but increases your odds of winning.
Pay attention to the amount you bet per line. Playing the maximum number of lines per spin at the maximum bet per line can add up big time. As stated in step three, the minimum bet on a 20 line machine costs 20 cents per spin, but a maximum bet of 10 cents per line equals a $2 bet per spin. Playing the maximum bet will increase your jackpot on a win, but will also cause you to spend more in the long run.
Increase your bet if you are winning, but decrease it if you are losing. Don't expect to turn a winning streak around by making the maximum bet. Gradually increasing your bet as you win will increase profits, and decreasing your bet while losing will decrease losses.
Change machines if you get one that is not paying out. While you might suddenly hit the jackpot on a "dead" machine, you might be more inclined to maximize your bets out of boredom, thereby decreasing your total winnings. Change machines as frequently as you like.