There are a number of factors that affect the way jackpots work. First, the number of reels can affect how likely you are to hit the big one. The more reels, the harder it is to hit it, so to increase your chances, play classic slot machines that only have between 3-7 reels. The second factor is the minimum and maximum betting limits. Releasing the maximum number of lines increases the chances of winning, but is more expensive than just playing one line. Some games offer up to 80 or more paylines!