Search engine optimization (SEO) and search engine marketing (SEM) are two important ways to promote your business to online customers. SEO requires making your site search-engine-friendly, and SEM involves targeting potential customers by purchasing relevant keyword ads on search engines such as Google, Yahoo and Alta Vista.

SEO: There are many ways to optimize your site so that search engines will list your site higher in their rankings. Start with the following:

• Links from other sites: Search engine spiders move from site to site across the Internet by following hyperlinks. The more high-quality and high-trafficked sites you have pointing to your site, the more important the search engine will think you are. Make sure to register your site with directories such as Yahoo (www.yahoo.com) and the Open Directory Project (www.dmoz.org).
  

• Internal links: Make sure your site is well-organized and easy to navigate. A site map will help visitors - and spiders - nawigate your site.
  

• Metatags: Metatags are hidden HTML directions for Web browsers or search engines. They include important information such as the title of each page, relevant keywords describing site content and the description of the site that shows up when a search engine returns a search. Make sure your metatags accurately describe your content.
  

• Keywords:Spider likely words or phrases that users might type into search engines to find your site. Make sure your content contains those!words or phrases, and include them in the title portions of your site and in relevant content.

• Search engine optimizers: Businesses often enlist the help of optimizers who specialize in improving the visibility of their clients' sites. Among other things, they'll register your site with major search engines, list it in the appropriate directory, write optimized content for your site and recommend changes to your site architecture.

SEM: The more targeted your advertising, the higher your ''conversion rate.'' Conversion rate refers to the percentage of ads that actually convert to sales or some other desired action (such as registration). One way to ensure that your prospective customers are qualified is to buy ads according to specific search engine keywords that a user might submit. For example, if you're selling a Minolta 60X digital camera, buying the keyword ad ''Minolta 60X digital camera'' will most likely give you better results than buying the keyword ''camera.''

Some terms get bid up quickly - for instance, you'll pay a lot more for a technology keyword than a knitting keyword. SEM, however, has a higher conversion rate than other online marketing methods, so it can still be a cost-effective route to take.

Make sure you have compelling ad copy luring people to your site. Provide a call to action to prospective customers to encourage them to click on your link. Also, make sure that you send prospective customers to a targeted page on your site. Your home page will convert fewer customers than a page describing the exact service that you promote in your keyword ad.

You generally pay for keyword ads on a cost per click (CPC) basis. Review the keywords you've purchased to ensure you're getting a good return on your investment. If not, try a different word or phrase. You can also try different ad copy or landing pages on your site to see what's more attractive to prospective customers.

Companies offering CPC programs include Google, Yahoo, AskJeeves, FindWhat, Kanoodle, Entireweb, Industry Brains and LookSmart.

Once you've exhausted your SEO and SEM options, there are a couple of other routes that will produce results. You can put together an online ad campaign by either buying advertising on sites that appeal to your demographic or trading ads with other sites. In addition, you can send out e-mail newsletters. Encourage customers to provide their e-mail addresses so you can contact them with useful information and promotions.