If you want to win at video poker, it is not enough for you to know the different rankings of poker hands and which beats what. Video poker is a game that requires you to make good decisions regarding your cards - and your cards alone. Because you have no human opponents, you do not have to resort to bluffing, value betting, check-raising, or moves that would be valuable in regular poker games. You just have to make mathematically sound decisions. And to do that, you should avoid making mistakes.
Minimizing the mistakes that you make is the way to win at video poker in the long run. First, you should not make obvious mistakes. If you already have a Two-Pair, you already have the average winning hand, so keep it. Do not throw away the 8-8-3 if your hand is AA-8-8-3. Just throw the lone 3 so that you'll get a chance to hit a Full House. If you have a Three-of-a-Kind already, as in 6-6-6-7-8, do not throw away two Sixes so that you'll hit a "longshot Straight". (The right play is to try to make a Full House or Quads.)
Remember that the money you save by not making mistakes is just as valuable as the money you win through sound play. So to win at video poker, you have to know the odds, or at least, when you are holding cards in your hand, you have to know which of your alternatives are the most probable to occur. For instance, if you are holding AAKQJ unsuited, you already have a Pair of Aces, but if you throw away an Ace, you might complete a Straight. But is it worth throwing an Ace away? There are only four cards that can help you finish the Straight (the four Tens) so it's not worth it. Just throw away the KQJ and hope that you hit at least one more Ace.
Many people think of poker as a gambling game, and casinos continuously exploit that fact. Many people around you make mistakes that you would not dream of making. These mistakes are the reasons why video poker is profitable for the casinos. People give up money every time they make mistakes in poker. For example, suppose that you have AAA-8-7. Everyone knows that the right decision, based on math, is to discard the 8-7 and hope to improve. The option to discard just the Eight or the Seven yields a smaller chance of improving. (The probability that you'll improve if you discard just the Seven or the Eight is 8.51%; the probability that you'll improve by discarding the 8-7 is 10.36%.)
Now suppose in your AAA-8-7 hand, you discard just the Seven, and you hit the Ace, then giving you quads. Does that make you a winner? In the short run, yes, but you made a mistake. You made a special type of mistake; the sort of mistake similar to the mistake you make when you draw to an inside "Straight in Hold'em". You may make that Straight, but still it's a mistake to do so. If you want to win at video poker, remember that good intentions matter more than good results.