I don't recommend using Frequently Asked Questions (FAQs) on intranets and websites. In modern web apps they're not the right way to help site visitors find the content they're looking for.
FAQs have been used for decades (or if I'm going to be a history pedant, centuries). Back then, they more properly filled a void left behind by real-time publishing through the Internet. For example, early NASA mailing lists in the 1980s would often include FAQs for new users, answering key questions, and allowing them to catch up and follow future mailings more easily. But you can imagine that even in that scenario time would make FAQs of dubious convenience, or even value.
Fortunately, we don't need this strategy nowadays. So when you're in the process of organizing and structuring your website content, keep the following in mind when you get stuck on content that doesn't seem to fit into a bucket, or even if you're deliberately planning to implement FAQs.
FAQ lists are typically too long, not scannable, and don't answer questions quickly. The nightmare for users looking for information is a giant list of random questions, in a seemingly arbitrary order. You may add categories and even a navigation to make them easier to search, but it won't matter as visitors still have to read every question in order to find what they're looking for. And if you're going to go through the trouble of creating a navigation structure, why not incorporate the content into your site using its navigation structure?
They can alienate site visitors. When information is hard to find, people become frustrated. So when a visitor doesn't find their question in your FAQ, they feel subordinated; marginalized.
They usually represent questions the site owner imagines their visitors will ask, not actual questions they want to ask. Let's assume an FAQ section has real worth. Even though you know your site visitors well, you can't know all of them; especially new or infrequent visitors who typically are the target for an FAQ section. You're not omniscient. And if you aren't periodically soliciting them for feedback and keeping the content up-to-date, an FAQ section becomes stale in a very short amount of time.
Most importantly, they become an "island of misfit content". This is especially true after the website is deployed and new content needs are identified. Anything that doesn't fit into the current information architecture gets thrown into the FAQ section. If you find content outliers the solution is to revisit how your content is organized.
When are FAQs appropriate?
If your site is focused on Q&A and you want to expose the most frequently asked questions based on analytics, and especially if your site relies heavily on search, go for it.
Another great use for FAQs is as a convenience on a content section landing page. So, imagine you sell cars, and you have a landing page for a section on financing. Including 3 (or so) researched FAQs as part of the content can help a large percentage of site visitors, and also set the tone for the type of information and level of detail they will find within that section.
In short, they can be great as supplemental content. But relying on them as a primary method for information discovery is a bad idea.
Resist and refocus.
When presented with content challenges, it's a great opportunity to revisit your content strategy and information architecture. Remember that if, for example, a visitor has a question about your services, navigating to your services pages should not merely answer their question through clearly and completely presented information. It should also expose them to other related information, potentially answering questions they didn't know to ask.
All of this should underscore the importance of diligence at the outset of a website redesign project. Start with user research and a thorough content review. And follow through with constant improvements through feedback and re-evaluation over time. You'll find that you don't need that FAQ section after all.