Your mattress, that is. It's the easiest way to avoid playing host to bedbugs.
Bedbugs, which are nasty blood-sucking insects, are a high-level threat in townhouses, apartments, college dorms and any other type of densely-packed dwelling where people sleep in close proximity. In recent years in particular, they've earned a reputation for toughness because they're becoming resistant to a lot of traditional extermination methods. Because bedbugs are so resilient, an infestation can only be reliably eradicated by extreme heat (which must be applied to every single fabric and textile-based product in your home, for certain periods of time) or chemical extermination. This is another situation in which hardware store chemicals are no help at all.
How do you prevent bedbugs from moving in? Well, you really can't. Contrary to popular belief, even immaculate hygiene and cleaning habits don't make you immune (and if you catch them from your neighbors, it doesn't necessarily mean you'll spot them on "Hoarding: Buried Alive"). But there are steps you can take to reduce your chances of an attack.
The easiest and least expensive way to combat bedbugs is to prevent them from penetrating your mattress. Bedbug-proof mattress sealers are fairly new products that allow you to place your mattress in a specially designed bag that doesn't allow bedbugs in or out. That's it. Bedbugs are known for burrowing -- that's how they get in your mattress in the first place -- but these covers are made from a special material that the bugs can't wiggle through. New bedbugs can't get in your mattress or around the seams, so you've deprived them of their favorite place to hide. Any existing bedbugs won't be able to get out or bite you through the cover, so they'll die a languid death over the next 18 months or so. (You can use this method to save your mattresses if you've already suffered from an attack...that is, if you aren't entirely creeped out by the idea of sleeping on an infested mattress.) For about $50 per mattress, you can rest a little easier.
Already infested? You know the drill. Alert your townhouse association -- they tend to take bedbug problems seriously because they spread so quickly. And if you get notice that there's a problem in your complex and your unit will be exterminated, cooperate with the instructions and methods. It's a pain in the butt, but it's better than getting bit by those little blood-suckers.