Use appropriate wording on pages so that the search will find items. For example, never use an acronym on a page without spelling it out at least once. Consider the user who may not be familiar with the acronyms used by projects and programs. Use metadata or other invisible text on subsidiary pages to identify the topic being discussed, if this information is not included on the page. When managing a spider that gathers pages from your intranet, construct filtering rules to make sure that the spider indexes as much as possible of the content you want and ignores as much as possible of the content you don't want.
Every intranet requires different filtering rules for spidering to be successful.
Additionally, you need to maintain content on a regular basis by checking logs to see whether the spider is indexing undesirable content and checking the index to ensure that it has found the desired content. The ideal spidering strategy for an Intranet is to start at a single page and follow links everywhere in the applicable DNS domain. Attempts to divide this domain into disjointed, separately-spiderable webs will almost certainly fail. Rather than index all of it yourself, use a META search interface that will forward a query to many different search interfaces and return the results in real time. A discussion of META search products can be found on Search Engine Watch.