There's tips and tricks to learn, but as far as normal blackjack goes, you want to get 21, ideally. It means you can't lose. To win, you have to get a higher card value than the dealer without going over 21. The dealer is required to stop asking for cards if they hit a certain value like 17 or 18. It shows in the game when they have to stop. Mostly everything else in the game is just craziness.