It's nice to see more people actively reporting suspicious content. There is in fact a function, specifically for this purpose. Right next to the other action buttons ('Quote', 'Multiquote' and 'Quick reply') is a warning triangle. If you click it, you'll be able to report the post and give a short explanation of your reasoning.
What happens next, is that all moderators receive an email with your reason, and a direct link to the post. This means faster dispatch and swifter justice. Also, a discussion thread is created in the quarantine, in the rare event that it needs discussion for one reason or another. It also keeps us all in the loop, and serves as an archive, in case we need to find out who has been naughty in the past.