Those who want to win the progressive jackpot should play as many lines as they can afford. This will maximize the amount of time you spend on slot machines, and offer you more chances to win the jackpot. Assuming you're just looking to have some fun, it's best to keep the number of paylines under 5.
How to tell when a slot machine will hit. You cannot tell when a modern slot machine will hit because the outcome of each spin is random.