Get a smaller trash can.
I know, I know, this seems like a backwards tip. Shouldn't I be telling you to get a bigger trash can, so you can put off taking out the trash for a few more days? That was what I thought at first, too. But I have learned something about myself: I will put off taking out the trash until I can't balance another item on the mound. Once a piece of trash tumbles off the pile for the fourth or fifth time, I will cave and take out the trash. This presents three problems when you have a big trash can: 1. You can't get the bag shut, because there's too much stuff in it, 2. The bag is too heavy to carry, and/or 3. The trash has been sitting in the bottom of the bag for far too long, and the lowest level of trash has liquefied, making a leak that much more nasty (and, proportionately, that much more likely).
So, buy a trash can that is just a little bit too small. It will make you take the trash out more often, and save you a lot of headaches in the long run. (But keep buying the bigger trash bags, for those days when you really need the extra trash space, when you can just take the bag out of the can and fill it to your heart's content.)
Bonus tip: If you live in an apartment building with a garbage chute, buy a REALLY small trash can. There's nothing worse than getting to the chute and realizing your bag won't fit, so make sure a full trash can will always fit.