Below are three tables showing how to play perfect blackjack strategy, along with a key for understanding whether you should hit, stand, double or split in any scenario. The tables all assume that the dealer always stands on 17 and that you are playing with 48 decks of cards.
Hard hands mean you don't have an Ace, Soft hands mean you do have an ace. Therefore, a 'Soft 16' means you have an Ace and a 5 (so it's 16 or 6; soft 16).


 Double if Allowed, or Stand 
 Surrender if Allowed, or Hit 

Hard  2  3  4  5  6  7  8  9  10  A 

48  H  H  H  H  H  H  H  H  H  H 
9  H  D  D  D  D  H  H  H  H  H 
10  D  D  D  D  D  D  D  D  H  H 
11  D  D  D  D  D  D  D  D  D  H 
12  H  H  S  S  S  H  H  H  H  H 
13  S  S  S  S  S  H  H  H  H  H 
14  S  S  S  S  S  H  H  H  H  H 
15  S  S  S  S  S  H  H  H  SrH  H 
16  S  S  S  S  S  H  H  SrH  SrH  SrH 
17+  S  S  S  S  S  S  S  S  S  S 
Soft  2  3  4  5  6  7  8  9  10  A 

13  H  H  H  D  D  H  H  H  H  H 
14  H  H  H  D  D  H  H  H  H  H 
15  H  H  D  D  D  H  H  H  H  H 
16  H  D  D  D  D  H  H  H  H  H 
17  H  DS  DS  DS  DS  H  H  H  H  H 
18  S  S  S  S  S  S  S  H  H  H 
19+  S  S  S  S  S  S  S  S  S  S 
Pair  2  3  4  5  6  7  8  9  10  A 

2,2  SP  SP  SP  SP  SP  SP  H  H  H  H 
3,3  SP  SP  SP  SP  SP  SP  H  H  H  H 
4,4  H  H  H  SP  SP  H  H  H  H  H 
5,5  D  D  D  D  D  D  D  D  H  H 
6,6  SP  SP  SP  SP  SP  H  H  H  H  H 
7,7  SP  SP  SP  SP  SP  SP  H  H  H  H 
8,8  SP  SP  SP  SP  SP  SP  SP  SP  SP  SP 
9,9  SP  SP  SP  SP  SP  S  SP  SP  S  S 
10,10  S  S  S  S  S  S  S  S  S  S 
A,A  SP  SP  SP  SP  SP  SP  SP  SP  SP  SP 
If rules differ from those above, you should look to play your blackjack somewhere else as you're sacrificing an even bigger edge to the casino. Put simply, you'll lose more money longterm by playing with worse rules than the above.
It's worth noting that even if you play the perfect blackjack game, with the perfect blackjack rules (where the dealer peaks if they have an ace), the casino edge will still be 0.42%. Your RTP (ReturntoPlayer) will be 99.58%.
When the rules change, or you veer away from best strategy, your RTP lowers and you win less/lose more over hundreds or thousands of hands.
There are only two ways to win longterm at blackjack:
1) Count cards: Very hard to learn, likely to land you in a lot of trouble
2) Learn to exploit bonuses and cashback via sites like Profit Maximiser
Ultimately, the only way to beat casinos is by using promotions to your advantage.