Grab everyone you can and have them work through your site. Start with your team first, to avoid the embarrassing moments; we all have mental lapses–it’s better to hear it from a colleague. Observe, discuss, use people from all different backgrounds, and look for different responses; don’t simply try to validate your own expectations. Make sure it works for you, for novices, for experts, for casual users, and for hard-core critics. Then, try it on a kid.