From the February 2011 issue of Entrepreneur
This is a very broad question so unfortunately it will be a broad answer.

1. Define your target market, ideal client and put a geographical component in this definition.

2. Develop your message to your target market, higlighting benefits, offers and solutions

3. Figure out the best vehicle and most cost effective vehicle to get that message to the target market.

4. Do it often and frequently

Hope this helps,