The Blackjack Hi Lo count system, also called Plus/Minus is thought to be a one level count (the count adds or subtracts one). The author of the system is Harvey Dubner who made Ed Thorp's Ten-count system much simpler.
The Hi-Lo system is a perfect start for those who have just started learning how to play blackjack and want to find a way to increase their odds. This method can be used in teams and can be used for any game of blackjack.
The basics of this count are so simple that if you know basic arithmetic you can learn how to use it. In order to use this strategy you have to memorize the numbers that correspond to group of cards in the game.
Small cards (2, 3, 4, 5 and 6) count as +1
7, 8 and 9 count as 0.
All the ten-valued cards (10, J, Q, K) and an A count as −1.
This system is balanced because if you count the whole deck you will end having zero. As soon as the game starts the count is 0, then you add or subtract 1 from it. When you do that you know the percentage of high cards in the deck. The higher the count is - the more small cards have been dealt, therefore big cards are about to come. You can get a good starting hand as well as blackjack and the dealer is more likely to bust.
When the count is small or negative this means that lots of high value cards have been dealt already and there are lots of small cards left in the deck. This situation favors the dealer as he is less likely to bust if he has 15 or 16 and hits.
If you lose the count while playing you can continue to use blackjack basic strategy and avoid risky bets.