You could start in a lot of ways. You can even just start out operating out of your trunk and just go door to door (I've done that). You have to build a customer base and then word of mouth will get you more business.
www.vistaprint.com can get you set up with some business cards for practicaly nothing. You pay like 8 bucks to get em shipped and they send you 250 of em. Really good deal. Just start handing those out to people and make sure you leave some with your customers so they can pass them on to their friends.
How big are you wanting your business to be? One of the problems I found with advertising too much is that if you aren't prepared for the business then sometimes you have to turn down deals. I had to turn down a deal for a guy that buys dozens of cars at auto auction each month. I simply can't handle that many cars unless I quit my job and did this full time. I plan on doing that sometime but not yet. I'm not ready to do it full time yet.