The best advertisement is word of mouth. Certifications won't cover you. If you screw up, or something dies and it's not even your fault, it's still your fault, certs or no. That's the way clients think. lol.

The next best thing is to pay top dollar for the leading listing under your category of the yellow pages. This option is expensive, but if you plan carefully you will do quite well. I usually find a well worded paid listing on the local buy and sell magazine works rather well too, but the last few weeks have been disappointing.

Tell your friends, and do good work for them. Don't sell your services cheap. There seems to be a notion going around that the more a tech charges, the better he is. It seems to work for some reason. Leave the $20/hour crap to the wannabes and little kiddies that are working out of their bedroom to save up for their next computer part or Xbox.

Another good way to get the ball rolling is to go work for a computer store for a year or two. They pay really poor money, but it's really good experience and it will get your show on the road.