Between each game. For example, how much do you have to wager? One game may start at a penny, while another requires a bet of $1 or more.
Do you understand payouts and the way they work? You definitely want to find games that pay a lot of money, even when you don't hit the jackpot.
Obviously, the more you win the better you will feel about continuing to play in the future.
There is a chance that you may become confused from time to time. If this happens, you need to know where you can turn for the right information. In most cases, you can find everything you need right on the casino's website.
If all else is failing you, remember this: practice makes perfect. The more you play any online slot machine the more comfortable you will become. Soon enough you will understand exactly what you are doing.
Even if you do not fully understand online slots right now, you can change this in the future. Once you know exactly what you are doing and what to expect, everything will fall into its rightful place and you will feel better about your chances of winning.