James Everett shares ten suggestions for building a successful, relevant, and frequently used wiki.

The first one is exactly what you should start with – Assess your needs:

As with any tool, evaluate what it is about the existing system that leaves the team unsatisfied. What are the obvious areas for improvement of your documentation system? Generate a list of criteria that would create the perfect tool for editing, storing, accessing, and tracking the project’s documentation.

Tip #5 emphasizes the importance of structure to organizing information and building good habits:

Make sure the first page users see presents them with the most pertinent info, based on their account. Wikis often support a variety of structures, including hierarchies, which are often easiest to follow for docs relating to a single project. Users build habits quickly; presenting them with a well defined structure right off the bat can create best practices organically.

(via MindTouch Blog).