I’m one week into a six-week course on search engine optimization, which means we’ve barely learned the difference between a search engine and a directory. But I wanted to pass along five valuable lessons I’ve learned so far.

1. The top 5 search engines receive more than 90 percent of all search traffic. They are: Google, Yahoo, MSN, AOL and Ask. The top three are pretty much neck-and-neck in terms of the audience they reach in a given month.

2. If you’re not listed on the first, second or third page of search results, you’re most likely not going to get any traffic through search.

3. The instructor of my class, Bob Viers, suggests steering clear of some sponsored links. “Research has shown that sponsored links that appear to the left or to the right of the Web search results are not very appealing to Web surfers.”

He suggests instead buying sponsored links that look like actual listings.

4. To see how people actually use search engines, check out Dogpiles’s Searchspy, which shows you what people are searching for at that moment.

5. Some search engines, including AltaVista, allow you to see which sites are linking to your site. Just seach for +link:yoursitehere.com. For example, here’s a list of sites linking to DesMoinesRegister.com.