When you are nearing the bubble, the common impulse of the player is to tighten up and make the money, and there is nothing wrong with this poker strategy if t your goal is to simply make the money.  However, middle stacks should be bullying short-stacks, by putting them all-in repeatedly and risking their going out on the bubble.  Say a small stack raises to 600 when the blinds are at 100 and 200. 

What do you do as a middle stack in the cutoff position?  The answer should be obvious: you raise with virtually any playable hand to raise the small-stack all-in.  It is almost guaranteed he will fold, especially if you make it aggressive to play etcetera.  I would place the bar at Q-J for raising all-in. 

This interweaves with Harrington's concept of "fly-swatting," where you should always put all-in a player who is raising who had 1/10 you stack.  The idea is that you have requisite folding equity in addition to live cards and the possibility of sucking out on a better hand.  You should thus always re-raise with a strong hand when a short-stack raises, putting him to a decision for his  tournament life right on the edge of making the money.  In this way you exploit the poker tournaments dynamics to your advantage. Now if you are the small stack the shoe is on the other foot, and you should be going all-in with any conceivable hand better than K-10 or something, given that you have an "M" value below 5.  This brings us to the extremely important concept of "M zones," Harrington's seminal contribution to tournament dynamic theory.  Throughout the tournament you have several "inflection points," where your M value changes zones.  The M value, or Harrington number, is the ratio of you stack to the sum of the BB and the SB, for example with a stack of 4000 and blinds at 100 and 200 your M would be 13.3. 

The higher the M, the better your maneuvering ability and the deeper your stack compared to the blinds.  According to Harrington, an M of 1-5 is classified as the red zone, 5-10 the orange zone, 10-20 the yellow zone, and 20 and above the green zone.  When your M is 0-5, you need to go- all-in with any conceivable hand, K-10 or better.  You can utility the folding equity of the larger stacks, who may mistake your all-in for a tournament stand rather than a desperate move.  But the seminal danger of waiting to go all-in when you are a short-stack is that, if you get blinded down, and then pick up J-J, even if you double up you will still be in danger, in the red zone.  Thus, it is critical to make a move more quickly than most people realize.  Therefore, when you are on the short-stack, you need to go all-in, if you pick up a hand such as K-10 or better.  Only in this way can you climb out of the danger zone and make the money.  Conversely, if you are big-stacked, with an M of 20 or above, you should be exploiting the short-stack's ability to go all-in with any hand and call with just about any hand provided, you have the aforementioned 10 to 1 superiority in poker chips, in line with "fly-swatting."  Thus, you should threaten middle stacks with extinction by raising them all-in and threatening them with reduction to small-stack status and the red zone that this entails.  Above all, the larger stacks should be hyper-aggressive on the bubble, exploiting the Harrington M-zone concept and the concept of folding equity, whereby you should raise rather than call all-in, since you have a chance for your opponent to fold if the former happens.  These concepts should prove vital to the developing poker players in deciding how to play certain hands on the short and big stacks.