[BluffTHIS!]

Most sites allow you to buyin for either the max or for as little as 20% of the max. I personally for many reasons always buyin for the max. But it is perfectly acceptable to buyin shorter either in order to stretch your bankroll so that you can play at a particular level, or because you believe it is a good strategy in general as Rolf has recommended in some of his columns. However, I think it is a mistake to buyin for the absolute minimum. This is because that although you are not paying any more in blinds than the max stacks, it nevertheless does cost you more to play in raised pots where you mostly fold the flop and are not in a situation to reraise allin preflop with aces. Then after you have paid all those preflop raises and finally get allin and double up, you have only gotten even. So if you are going to buyin for the absolute minimum, then you should just play supertight and only seek situations to get allin preflop with aces or maybe kings with very good sidecards when you don't believe a preflop raiser has aces. So I would recommend buying in for 40%+ in order to be able to make something, and so that in smaller pots you are able to bluff effectively if the situation warrants it.

Also SilentAcorn's advice about seeking tables with relatively small pot sizes would especially have merit if you are buying in for the min. This is because I see everyday on the 1K/2K tables where someone playing that short stack finally gets the big AA and reraises allin. The only problem is that it is a fairly loose and aggressive table, and the rest of us just go ahead and call $200 or $400 and take the flop 5 handed and pretend that player isn't there. With aces you ideally want to be headsup, but on those kind of tables that won't happen. Of course if you hit the board good then you really score, and you can always hope that an overly aggressive player with only an overpair and a gutshot bets big into a dry side pot driving the other players out, and your aces win unimproved. But the majority of the time you will simply be rebuying on those aggressive tables because any kind of hand that could get there will.