You must count the cards that come from the shoe, and know how many cards of each type remain in it. This provides you the probability of next card dealt.

Study card counting techniques to predict when the card deck is more likely to deal face cards and aces. Then bet more when there is better chance of getting 21.

The only way to beat the house at blackjack is not to play. The house always wins. You can gain an advantage by counting cards, but it's not advisable.