Tamburin High-Low or How to Win at BLACKJACK!
Basically this is a card counting methodology for black jack developed by Henry Tamburin.

How it works
Basically as you play blackjack you keep a running total of how many low cards versus high cards have gone by. You only have to keep track of 1 number called the running count. Different systems have different values for the cards, but Tamburin High-Low is great because it is balanced (all the card values in the deck add up to 0) and it is SIMPLE. For every card 2-6 that you see, add 1 to the count. For every card that is a 10 or an Ace, subtract 1. For the other cards do nothing.

Card   Value
2    -   1
3    -   1
4    -   1        TrueCount = RunningCount / # decks
5    -   1
6    -   1
7    -   0
8    -   0
9    -   0
10   -  -1
J    -  -1
Q    -  -1
K    -  -1
A    -  -1

So once you have this running total you are counting cards. Now you simply raise your bet when the card count is really high, and likewise lower your bet when the card count is really low. To really be able to tell how much you should raise your bet, you might need to know the true count. This is the running count divided by the number of decks left in play. Use the True Count to judge how much to alter your bet by.

This works because you like the deck when there are lots of 10's left. If there are a lot of cards with value 10 left then you are more likely to know what the dealer has, and you are more likely to get a good hand. The dealer is also more likely to bust on a bad hand. A huge benefit is derived from extra 10 value cards when you double down or split cards. Then the extra 10's can really pay off.

Using a system like this it is possible to make the odds actually work in your favor! This is hard to do, however, and technically not allowed by the casino. So don't be obvioius. If your really interested, buy a book on it and practice at home.