There are two major ways to "optimize" your site so it's most likely to show up in a potential customer's search.
First, carefully identify the words and phrases your best prospects are most likely to use in searching for whatever you provide. Each page should contain two or three keywords that you want people to use in finding you. (But don't list those words dozens or hundreds of times in attempt to show up first in search results; that's called "keyword stuffing" and it's considered cheating.) Choose keywords that are simple, coherent, and consistent with your other marketing campaigns, and be sure to list them in metatags as well.
In addition, get specific. Phrases like "limousine" won't set you apart from the pack. But adding your city and state, for instance, might help land your site higher in the results for searchers using those terms. In addition, keywords--not just your company name—indicating what your company does should appear in the title bar atop your site's pages. This tells users at a glance whether they've found the right site.
Secondly, keep in mind that search engines love links . The more sites linked to yours, the higher it's likely to rank in search results. Links are essentially the same thing as votes. From a search engine's point of view the more votes you have, the greater the indication that there's high-quality content at your site. So keep building your network of relevant links.