It�s always a nice situation to be in, the big-stack, the chip-leader. You are in front and dictating play, this what Poker is all about...

Unfortunately, there are many players who will play incorrectly once they have won a few pots, squandering their lead and money away.

Being the �big-stack� basically gives you the ability to knock-out any other player on the table. For the sake of this article I will refer to tournament games, as with ring games your chip stack only reflects what you have taken into to the table, and can be changed after every hand.
Firstly, how much of a big-stack are you? You could be marginal chip-leader, or a big chip-dominator. The mistake many players make is the method they use, to work out the size of their stack. The correct way is to compare your stack to the total amount of chips on the table, and not what 2nd, 3rd place etc have got.

Early on in a tournament
Another common mistake is to overvalue being the chip leader at the beginning of a tournament. Firstly, with the blinds so low anybody can push their way back up. Your lead will not be that great (again comparing your chips to the total at the table).

There is little value in bullying the table early on, the confidence that winning a few early pots can bring tends to encourage people to do this. With your chip lead not that substantial, if you were to lose a big pot you would most likely be a below-average stack. And with the blinds so low, it is unlikely that players will be bluffing at you, and also give little value in stealing pots from your opponents.
It is always a good idea to build up a tight table-image in a tournament, especially SNG�s. This can then be exploited at the later stages when the blinds are higher and the pressure for the prize money is on.

Sit on your stack and be comfortable with your play. Stick to a tight hand-selection but play your cards strongly.

Late on in a tournament
Likewise the same mistake some players make is to play conservative with a big-stack when the prize money is insight, in knowledge that they can be guaranteed to walk away with a piece of it.

Although this often seems like a clever decision to make, it is often the most common decision made by your other opponents. Therefore now is the time to start pushing your chips around. With the blinds higher and play tightened right up.

The game will normally be a case of 'cat-and-mouse'... the bigger stacks looking to knock-out small-stacks, who are looking to double up. You will see quite a few pre-flop all-ins.

Time is on the side of the big-stack. The small-stacks need to make a move sooner rather than later or they will be simply �blinded-out�. So by stealing their blinds and forcing the issue they will be more likely to choose a weaker hand to make their move and go all-in. Don't let them wait around to catch a premium hand and double-up, giving you more competition to deal with.

Playing aggressively at the end of tournaments is risky and can end in frustration, however due to the way your opponents will play it will be more profitable in the long run. However, look out for other players using the similar tactic, as quite often two players with the same strategy can run into each other, causing disastrous results.  
So remember, being the big-stack requires as much strategy and technique as playing with any other sized-stack. If you know how to adjust your game to take the greatest advantage of your lead than the rewards will be coming your way.