Small notes.
Clearer systems.

Measure the part that matters

A useful measurement answers a specific question. Before collecting more data, write down the decision you want to make and the observation that would change it.

Keep the original conditions close to your results. A number becomes much more useful when you know what was running, what changed, and what stayed the same.

Make the next change smaller

Small changes are easier to understand and easier to reverse. Give each change one purpose, check its effect, and leave a short note for the next person — including your future self.