A quiet place for observations, useful habits, and things worth remembering.
Write down the observation first. Add enough context to make sense of it later: what happened, what you expected, and what you might try next. A short note you can find again is more useful than an elaborate system you never use.
Separate a result from your explanation of it. Keep the original observation when you change your mind. This makes the next decision easier to understand.
Prefer a small number of clear parts. Give each one a purpose, keep a copy of what matters, and check that you can put it back together.