Most websites have terrible search engines. It is true that programming the searches is not an easy job at all and it take a lot of time and effort on your part to include a search engine in your site. However, it is better not to include search engines at all than to do it badly.

Stick to Conventions
Most successful search engines such as Yahoo, Google and the like follow a set of conventions for the display of search results. It displays large title, blue links, followed by the page's description, and the URL. For e.g:

Title of search result
… the text contain the keyword which was searched. The keyword is always in bold…
www.sample.com/example/101

The most relevant result is displayed first. In case there are too many results, they are divided into pages. The search engine remains at the top in case the visitor want to change the keyword and search again. There is also an advanced search link for the more complicated queries.

To learn these conventions, the best way is to study the best search engines in detail. Don't think that it is wrong to copy another search engine as all of them are copies of each other, in one way or the other.

Learn from PageRank
Google ranks the pages according to the popularity of that link. But it is not used too often as the page ranks can be easily distorted. However, it is a good way to search across your own website where the content can be controlled. It works better than the way of counting the number of times the keyword appears on the page.

Installing Search Software
Writing your own site's search engine is a time-consuming and difficult task. A better way is to take an existing one in the same languages as your site and adapt it for your own site. Some good places where it can be found are freshmeat.net and sourceforge.net.

Outsourcing Search
Another good way to avoid too much trouble is to outsource your site's search. This makes the user go to the result page of an external search engine. This method is becoming very popular these days. These services are offered by all major search engines such as Google, Yahoo and MSN.

However, this method should be used only when the you don't have enough time and resources to create your own search engine, as it send the visitor back to the web, which may force them to leave your site.