As with most household pests, the termite is absolutely fascinating - one of the most complex bio-systems imaginable. Here's a simple explanation of their reproductive cycle - mind-blowing stuff.
http://animals.howstuffworks.com/insects/termite2.htm
First, you must diagnose the problem. If you don't have a termite problem, you may be spending money unnecessarily. While it's always best to err on the safe side, many homes in the metro DC area were built on a semi-permanent film of various termite control chemicals, from chlordane (now banned) to dursban (ditto) to termidor. If the former was applied to your lot before the slab was poured, you should never have termites (unless you add an addition or otherwise disturb the foundation/soil). It would be very unusual for you to have a termite problem without seeing some kind of symptom. The colony will send out thousands of flying reproductive swarmers - this is your best chance at discovery. Do a google search to see how you can distinguish termite swarmers from flying ants. Speaking of which, a wood deterioration problem may not necessarily be a result of termites - carpenter ants can do almost as much damage.
You can also inspect for mud tubes - termites leave the colony to find food (ie: your house), but must return to the colony in the ground. They won't travel out in the open so they construct little mud tunnels - also a good chance for discovery.
If you suspect you do have termites, definitely hire a professional. It simply isn't worth the risk of ignoring it or handling it on your own. In the Metro DC area, there are several good ones. I use Western, and they have excellent customer service, vastly imroved over the years. Like any reputable pest control company, they guarantee their termite program. Be prepared to shell out several throusand dollars, and then an annual maintenance fee.