Get to know your audiences
Before you build a site, you need to know who you're building it for. Who are your primary and secondary audiences? For large sites with multiple audiences, the audiences themselves can even provide the basis for your architecture’s top level. For example, a typical faculty's website might have these sections:
About us | Prospective students | Current students | Research | News & events | Contact
Dividing your architecture by audience also gives you a chance to tweak your messaging for different people. For example, undergraduate and graduate students likely want different information, so they may appreciate an admissions-oriented site that triages them right away and addresses their individual needs separately. You may also want a more promotional tone for externally targeted content, and a more informational one for your internal audiences.
Learn how your users think
This might sound odd, but it isn't all that important that these groups make sense to you.  What matters is that they make sense to your users. If they can't find your content, you may as well not be writing it.
For example, you may think about your faculty's services in terms of which unit provides them. That probably makes a lot of sense from, say, a budgetary perspective. Â But your student-heavy audience doesn't care which unit does what -- and if they have to go to each unit's section of the site to find a complete list of services available to them, they'll likely either get frustrated, give up, or both.
For a fresh perspective, you may want to run a quick card-sorting exercise. In a nutshell, you take your list of content, write each of those items onto an individual card, and ask a focus group of your audience members to sort them into piles and sub-piles that make sense to them. With a little finessing, those piles can then become the basis of your site's new architecture.
For more information, see our User experience toolkit.