Kyle Soucy and Holly Phillips' talk at the IA Summit 2010 in Phoenix
Rite method: test and then make changes immediately (formalized by the makers of Age of Empires). However this isn't practical in a context where the whole team needs to be involved.
Don't integrate usability into a gantt chart/waterflow based method, because it holds people up. Instead have a usability testing day every two weeks, which might be about anything.
Don't keep religiously to usability scripts. Interview the participant beforehand and get an idea of how they actually use the site. Then base the test around that, so that the usage and the motivations are more genuine. Be comfortable with chaos and improvisation.
Don't write a report, nobody has the time to read them.
Debriefing
Do the day after the tests
Have the whole team be there (in-person or by phone) and show them all the tests.
After each test is shown, ask everyone to quote something the participant said or describe something they did, and then give an implication from that worded in one of the following ways
How to... (e.g. "how to make that work")
Wish for...
What if...
This keeps the discussion on-track and data-based. It's unnatural at first so a good moderator is needed.
http://ethnio.com is a good software for rapidly recruiting usability testers.