When it comes to website navigation, there are a few basic tips that should be followed. Make it simple, make it easy, make it spiderable!
1. Provide alternative navigation if you are using JavaScripted drop downs or rollovers.
2. Consider bottom placed navigation to supplement your page top navigation.
3. Always have a site map and link it from every page.
4. If your website is over 15 pages include a site search feature for easy navigation to content.
5. Place your top level navigation on the left or top. If you place top level navigation at the top, use the left to place additional links.
6. Text based navigation versions are best. Consider CSS styled navigation instead of JavaScript which search engines cannot read.