Learning what the game actually is.
WHY IT IS ESSENTIAL
You cannot see your own game as a new player does, ever.
WHO TO TEST WITH
People who have not played it People who are not friends, eventually People from the audience you intend
WHAT TO DO DURING A TEST
Watch, and say nothing.
WHY SAYING NOTHING MATTERS
Any explanation you give is one the released game cannot give.
WHAT TO RECORD
Where they hesitate What they misunderstand Where they stop What they say unprompted
WHAT TO ASK AFTERWARDS
What they were trying to do What confused them What they expected to happen
WHAT NOT TO ASK
Whether they liked it.
WHY
People are polite, and the answer is uninformative.
WHAT TO BE CAREFUL WITH
Acting on a single person's preference Confusing a suggestion with a problem
WHAT THE RULE IS
Players reliably identify problems, and unreliably identify solutions.
WHAT TO DO WITH SUGGESTIONS
Find the underlying frustration, and solve it your own way.
WHAT TO TEST REPEATEDLY
The first ten minutes, which determine whether anyone continues.