To design intranet navigation, find out users' mental model of potential content by running card sorting tests. Does an expense report form belong under HR? Finance? or a forms category? You'll only know the right answer after card sorting. Here's how:

• Make an index card for every piece of content. Limit it to 100 cards.
• Run 4 or 5 sessions with 3 or 4 users each.
• Ask them to group the cards in piles of related content. Piles can be as small or large as they want. If they want, they can also group the groups.
• When they're done, review each group for anomalies. Then ask them to suggest a label for each group.
• Collate the results to inform your navigation design.

Combine card sorting with your knowledge of business objectives, user goals and usability best practices to design intuitive navigation for your intranet. Make sure to test your final navigation design with a paper prototyping session.

Other resources:

• Here's a Word template for creating card sorting labels. I print onto Avery 5262 labels and stick them onto 3-1/2 by 5-inch index cards.
• Try using this frequency-of-content-use survey at the beginning of your card sorting sessions. You'll gather useful data and your users will familiarize themselves with the content they’ll be working with in the card sort. Compile the results with this Excel template.
• This excellent white paper provides in-depth information on card sorting.