When you are playing limit Texas Hold'em, there is one primary directive that takes precedence over every other bit of poker advice you have ever learned: you need a strong foundation. A strong foundation means picking the right cards to play pre flop. If you start off with the wrong cards you are going to end up loosing money in the long run. Picking the right cards means making money, or at least increasing your chances of making money. This may sound like an empty bit of advice; after all, shouldn't you always pick the best starting hands, regardless if you are playing limit or No Limit Texas Hold'em? Most of the time, yes, but it becomes very, very important in limit above others, because you do not have the power to force other players out of the hand.
Lets say you are playing No Limit Texas Hold'em and you have a Seven Two off suit, one of the worst possible starting hands in Hold'em. You are in late position, the limits are low, and you limp in with a call, hoping to do a little speculation. The big blind stays in and you are heads up to the Flop. Even if you totally miss the flop, you can take a stab at bluffing the pot with a half-pot or full-pot sized bet; your big blind opponent may have checked his way in with garbage, and if so, is not likely to stick around. Take this same situation in a limit game. If you want to try and represent a bluff, the best you can do is throw one bet at the pot and, unless the big blind only has that much left in his crippled stack, he is going to call with just abut anything. The problem with limit is that players stay in much longer than they due when the pressure is being applied, like in No Limit.
Limit poker can be a profitable game, but you absolutely need to have a strong foundation to make it work.