While designing the navigation for your site keep the following points in mind:

• Organized LinksMake sure your links are well organized according to the order of importance. Visitors should be easily able to find what they are looking for under different categories.E.g. All our main links are found on the top i.e. our services, products,portfolio, resources etc.Other interesting links are found on the right of the page. These are common and consistent throughout the site.Finally if the web page belongs to a guide E.g web design guide you will find the related links below the right menu and also at the bottom of the page.Note: Related links are very important as visitors coming to a particular page will probably be interested in more information you have under the same topic.
• Clear and ProminentOnce you have decided on your navigation links, you need to think of the best place to put them. Navigation should be clear and consistent. Try to design your navigation on the top or on the left as these are the first places our eyes go to. Also locate the primary links high enough on the page so that they are visible without scrolling. Navigation images should be seamlessly integrated into the site design. Avoid putting navigation links at the bottom of the page as visitors will need to scroll right down to see the links. If you like you could put the important links at the top AND bottom of the page just to make sure your visitors don't miss the link.
• ConsistentNavigation should be clear and consistent. The important links of your website should be on every page, in the same location, and in the same sequence. Don't confuse your visitors by putting your navigation links in different places in different pages.
• Easy to understandMake your links easy to understand and to the point. Usually you won't have enough place to have long links so make use of the space wisely. Visitors need to know where they will go on clicking on a particular link, so make sure your links are understandable or nobody is going to click on your links, which will defeat the purpose of designing a good navigation system.
• DHTML MenusIf you have a large number of links under categories and sub-categories you could use navigation menus to organize your links. There are many cut 'n' paste scripts available on the Net that you could use to create great navigation systems. A favorite resource center is  SimplyTheBest.net, you'll find tons of useful navigation menus that are very easy to install on your site.