A passage in a book I was reading today reminded me of the importance of simple checklists in testing.
"NASA had learned how to put a man on the Moon: by using checklists."
(Kirshner, R. P. 2002. The Extravagant Universe. 1st ed. Princeton: Princeton University Press. p246.)
Gene Kranz, former flight director for the Apollo 11 lunar landing, talking about checklists:
"I always had a checklist on my console. When I was under stress, I would always go through the checklist. Get the data, call the backups in, start running d-logs (data logs), etc. So that carries you through the first moments of this crisis. It also carries the team through these first moments of the crisis. So you get through."
(Asaravala, Amit. NASA Veteran Weighs In on Launch. Wired News, Jul 25, 2005. p2.)
As a tester, you may be the closest thing to an expert on how an application should behave. Remember to write it down! If I had a nickel for every time some subtlety was missed due to my sick days, vacation days, blonde days or simple forgetfulness, I would be a much wealthier man!