Social media. Search the web and you'll get a plethora of "how to's" etc...most of them are free and will save allot of money for you. You'd be surprised how many people type in "bbq caterer, spartanburg, sc" into google. If you can get it to where you pop up first, its a gold mine. I agree with grizzle though, business cards are a great investment, and guess how many you'll need and double it. The more you order the more you'll save. Also look into branding yourself and you product. Coozies are cheap and everyone loves them and depending on your budget you can do all kinds of things with shirts etc...
Good luck and have fun!