After the debriefing, it’s a good idea to summarize this month’s testing in a short email. By short, I mean it should take no more than two minutes to read—and no more than 30 minutes to write. Think bullet points, not paragraphs.

Designers are often reluctant to show things that look unfinished. But users may actually feel freer to comment candidly on something that looks rough, since they know it’s still subject to change.

For reasons that aren’t entirely clear, this transformative effect is much more pronounced when you watch tests live and in person than when you watch clips or a recorded session. It’s like the difference between watching a sporting event live on television and watching a replay later: “live” is just more compelling. And when you attend a session with others, you also benefit from the shared group experience and the opportunity to compare observations during and between test sessions.

Most people think that all users are just like them when it comes to using the Web. Watching real users gives them that eureka moment: they’re not all like me, and in fact they’re not all like anybody. I like to say that watching usability tests is like travel: it’s a broadening experience. You realize that the rest of the world doesn’t live and think the same way you do. This profoundly and permanently changes your relationship to users, making you a better developer, designer, manager, or whatever you are.

One important consideration: the observation room and the test room should not be right next to each other. You don’t want the participants to hear group laughter (or collective groans) that are in synch with what they’ve just done. Very bad.