Playing Texas Hold’em heads up against a single opponent requires a completely different strategy than playing at a full table. While some players may choose a heads-up game on the internet, the most common situation is during tournament play when it gets down to the final two players. Many players I have talked to tell me that they have the most difficulty adjusting to playing heads-up, and are not very successful when put in this situation. The most common reason for this is that they are used to playing a tighter game. In a heads-up situation, you can’t play tight and expect to win. You must loosen up. When you are playing heads up you can’t afford to wait. Many times it comes down to who can steal the most blinds. Therefore you must loosen up and call more or you will go broke.

Q-7 is called the computer hand because computer simulations show this hand will win 51.77% of the time heads-up against a random hand. So with this hand or any hand higher than this one, you are almost forced to play. A small pair or even a single Ace or King can be a big favorite in heads-up play.
In the small blind you can actually win (depending on your opponent’s skill level and strategy) by raising with every hand. If the blinds are, let’s say, $50 and $100, that means that there is $150 in the pot. The player on the button is the small blind and must act first before the flop. If you raise by putting in an additional $150 and the big blind folds more than 50% of the time, you will ultimately show a profit. If your opponent turns out to be more aggressive and calls more than 50% of the time or re-raises, you need to adjust your strategy accordingly.

In the big blind, suppose you only call with the best 33% of the hands that you are dealt. Now your opponent can raise from the small blind every time, and if called by you, not bet the flop unless they flop a good hand. When this is the case, they are going to win $150 two out of three times. Plus they are going to win other hands that play out. Your opponent will actually lose $150 less than one out of three times.
You need to judge your opponents. Poker is a game about making judgments. You need to test the waters by doing the raising and being the aggressor. If you find yourself in a game with a passive player, aggressiveness will beat them. If on the other hand your opponent is also aggressive, you will have to use some discretion and vary your play.

Playing heads-up poker is a lot like playing “chicken”. You will need to bluff more before the flop and sometimes fire away after the flop with nothing. With just two players there will be many times when the flop doesn’t hit either player. Many times it is the person that acts first who will win the pot. Just remember that occasionally your opponent will have a legitimate hand. Although you don’t want to be bluffed out of a pot, you will sometimes have to give it up to save your self from elimination.

The size of your chip stack makes a big difference in how you play as well. If you have a big stack, you can be much more aggressive and your opponent might be inclined to fold more often waiting for a big hand. While this may work, there will be a time when they are forced to make a stand. Although you want to keep the pressure on, you also don’t want to double up your opponent too often or you will find yourself with the short-stack.
Beware of the limper. Players limp in from the small blind for two reasons: They are either trying to see the flop cheaply or they are trying to trap an aggressive opponent. Again, this calls for judgment on your part. Your objective in heads-up play is to try and extract the most money from your opponent. If you have a big hand and know your opponent will raise, then you can limp in and try for a check-raise.

Becoming a proficient heads-up player requires practice. You can practice in the heads-up rooms on Full Tilt poker. You can also get together with a friend for some heads-up practice. Do it by starting with equal stacks, then with you being short-stack, and then with you being big-stack. It will teach you how to vary your play in all 3 situations.
I hope this helps!