Despite the cliches, if you build it, people will not necessarily come. If you build a better mousetrap, the world will not beat a path to your door.
How will people -- customers -- know that you built the baseball field in the middle of a corn farm or a better mousetrap?
You have to get the word out. You can try word-of-mouth, which marketers sometimes call "viral marketing". That works sometimes. You probably don't have money for a big ad campaign. Lots of dot-coms that advertised on the Super Bowl during the technology boom failed because they spent too much money on advertising and marketing.
What you need to do is make a plan. Figure out who will buy your product and what you need to tell the potential customers about the product or service. Then, figure out the most efficient and effective way to get that message across to the target.
This can be PR -- putting articles into papers, contacting local news TV and radio stations. Or it can be going to trade shows and running small ads in the trade press or getting articles into the trade press.
The most effective and most essential thing you can do, however, is to create a website. It can be simple. But if you optimize it for the search engines, you'll get traffic. You can always refer your potential customers to your website so that they can read your story and see your products or understand your services.
See the article on search engines and local search that is in my list of articles on the right. Free local listings can be highly valuable for a start-up.
Contact me with marketing questions or comments - firstname.lastname@example.org.