Understanding your point of view (persona, etc...)

All testing is done from a point of view. Some teams call these personas. For each round of testing you're doing, it can be helpful to explicitly state your point of view up front. Are you taking the point of view of the customer? The point of view of a sys admin? The point of view of a developer who's going to need to triage an issue in production? The point of view of a hacker? Whatever your point of view is, try to keep it clear in your mind as you're testing. If you're keeping test notes, write it down in your notes.

Each point of view will have different strengths and weaknesses based on what you're testing. After you're done testing, ask yourself what you would have done differently (if anything) based on a different point of view. If you feel you might have missed something important, capture that test idea somewhere.