As a professional webdesigner you should always make your visitor to move smoothly through your site. They should be aware of where they are and where they can go.Your website should be flexible. You can achieve this by implementing proper navigation scheme for yor site.
Your navigation can be considered as a road map for your site. If your site is poorly built for navigation then there are much chances of loosing visitor, if they get lost in your site.
Tips for Web site navigation :
Title: All navigation links should have a short and descriptive title making it easy for the user to understand where it links.

Importance : The primary navigation should not have more than 6-7 links. Keep only the most important links in the primary navigation and leave the rest for the secondary navigation.

Uniqueness : Always try to make your primary navigation links more unique by using some graphics or different links style.

Alternative link : If using graphics or javascript links, a text alternative should be available. Some people might have the graphics turned off or javascript disabled when browsing the Internet. In such cases an alternate option should be available.You can have a text menu and the bottom of the page could be included.

Keep it minimum: On every page there should be a reasonable number of links. Pages with 20-30 links are harder to use than pages with 10 links. Visitors don’t have the time to click on all of them to see if they are interested in the information secluded behind them. The best approach is group similar links in categories and let people discover them click upon click.