1.Anticipate User's needs

Your users come to your site for specific solutions to specific problems.  The navigation of your site (all aspects, not just just menus) should anticipate the needs of your users.

2. Meet user expectations.

Users expect to see “Home”, “Site Map”, “About Us,” and “Contact Us.” If the main menu is already bulging at the seams you can create a separate static menu dedicated to these. Stick it the top or bottom of the page where it is easily seen by the user but doesn't clutter the page.

3. Contain a maximum of 5 items (maybe 6)

In the movie “Moscow on the Hudson,” Robin Williams plays a Russian defectee. In one scene his character makes his first trip to an American supermarket to buy a can of coffee.  Upon reaching the coffee aisle he is confronted with endless choices of different brands of coffee. He becomes so overwhelmed he has a panic attack and is taken to the hospital.

Nothing shouts "amateur" like a menu with 15 items.  Don't give your users too many choices. 6 or more items will bog the user down.  If the user gets frustrated they will move on to a different site.

If you cannot avoid having more than 6 links, here are two possible strategies.

1. Divide and conquer.  Create more than one menu.
2. Place "Spacers" in the menu.  So the eye of the user can process the items in bite size pieces.

4. Anticipate user's needs with area specific menus.

Create separate menus that anappear at the appropriate  of your site.  Below is was originally a flyout menu image example

5. Be Well Labeled.

When your users reach your site, they immediately scan it to find the links to the information they want.  If your site requires several menus on the same page, make sure it is obvious what each is for.

Furthur Reading:

http://www.digital-web.com/topics/navigation