If you want to play blackjack it is extremely important that you at least know the basic strategy. Instead of guessing or playing with 'gut feelings' you can make the basic plays for every possible situation. Of course counting cards is much better than simply going 'by the book', but not knowing to count cards is by no means an excuse not to know how to play accurately. Blackjack is a game that's built on making the best possible play in the long run. I've heard many time players telling me that every time they stood on '16' against a dealer's face card the dealer busted, and every time they hit a '16' against a dealer's face card they were busted. That might have been true, but unless you count cards and know that the deck is very favorable ('loaded' with 10-value cards), the best thing you can do is hit a '16' against a dealer's face card. Although you're likely to lose, you're likely to lose more if you stand.
Basic strategy is the best way to play any possible situation, without any knowledge of the distribution of the rest of the cards in the deck. Shown below are basic strategy charts for single and multiple decks, where dealer stands or hits soft 17, and also a chart for european blackjack. You can use Blackjack 2021 real-time analyzer to see that it gives you the same results initially, but changes according to cards taken out of the deck. If cards are taken out of the deck and the data is applied to Blackjack 2021, you'll see the effects of professional card counting on decision making. Simply put, you can play the best possible plays if you use Blackjack 2021 correctly. Start learning blackjack by memorizing the blackjack chart that corresponds to the blackjack variation you're likely to play. I recommend the most common one which is multiple deck game (4 decks or more) where the dealer stands on soft 17.

To use the basic strategy charts easily look up your hand along the left vertical edge and the dealer's up card along the top. A represents ace in both cases. From top to bottom are the hard totals, soft totals, and splittable hands. Rule variations might have an effect on some borderline situations. The most flexible rules are the number of decks, whether the dealer hits or stands on a soft 17, and whether doubling is allowed after splitting two identical cards.

Key to table:

 H  = Hit
 S  = Stand
 D  = Double if allowed, otherwise hit
 Ds  = Double if allowed, otherwise stand
 P  = Split
 H/P  = Split if allowed to double after a split, otherwise hit
 D/P  = Split if allowed to double after a split, otherwise double
 S/P  = Split if allowed to double after a split, otherwise stand
 H/R  = Surrender if allowed, otherwise hit
 S/R  = Surrender if allowed, otherwise stand

A great way to memorize the basic strategy is notice patterns and to try to understand why you should play every situation as the chart says. Then make flash cards and go over and over them until you know it by heart. Don't deal out cards to yourself randomly because soft totals and pairs will not come out often enough to test your knowledge. Unfortunately, many people don't believe in the basic strategy because they once took the advice of someone who knew it and then lost the hand. To make things perfectly clear, YOU WILL NOT WIN EVERY HAND WITH THE BASIC STRATEGY! In fact, in the long run, you won't even win half your hands. However, while you will have short term ups and downs, over the long run you will roughly break even using it. There are two charts depending on whether the dealer hits or stands on soft 17.

Single Deck:

Key to table:  H  = Hit
 S  = Stand
 D  = Double if allowed, otherwise hit
 Ds  = Double if allowed, otherwise stand
 P  = Split
 H/P  = Split if allowed to double after a split, otherwise hit
 D/P  = Split if allowed to double after a split, otherwise double
 S/P  = Split if allowed to double after a split, otherwise stand
 H/R  = Surrender if allowed, otherwise hit
 S/R  = Surrender if allowed, otherwise stand

Double Decks:

Key to table:  H  = Hit
 S  = Stand
 D  = Double if allowed, otherwise hit
 Ds  = Double if allowed, otherwise stand
 P  = Split
 H/P  = Split if allowed to double after a split, otherwise hit
 H/R  = Surrender if allowed, otherwise hit
 S/R  = Surrender if allowed, otherwise stand

Four or More Decks:

Key to table:  H  = Hit
 S  = Stand
 D  = Double if allowed, otherwise hit
 Ds  = Double if allowed, otherwise stand
 P  = Split
 H/P  = Split if allowed to double after a split, otherwise hit
 P/R  = Surrender if allowed, otherwise split
 H/R  = Surrender if allowed, otherwise hit
 S/R  = Surrender if allowed, otherwise stand
European Blackjack: The following basic strategy chart is specifically for European blackjack. As a rule, the dealer initially gets one card and after the player makes his decisions gets the second card. If the dealer has a blackjack the player loses total bet including doubled or split cards bets.
The most common European blackjack rules are:

• Six decks (the chart is accurate for 4 to 8 decks)
• Dealer stands on soft 17
• Player may only double on hard totals of 9, 10, or 11
• Player may double after a split
• The house edge under these rules is 0.62%.

Key to table:

 H  = Hit
 S  = Stand
 D  = Double if allowed, otherwise hit
 P  = Split

In some casinos in the UK, splitting fours, fives, and tens is not allowed. This only affects the basic strategy plays with fours. Therefore in the UK always hit two fours.