Think first: Don't make assumptions, don't hide doubts, don't take sides silently. Ask if you're unsure; present all interpretations if there are multiple; speak up if there's a simpler approach.
KISS: Write only the minimal code needed to solve the problem—no extra features, no unnecessary abstractions, no defensive coding for impossible scenarios. Rewrite if you can compress 200 lines into 50.
DRY: Abstract only after repeating three times; copy twice, don't reinvent the wheel prematurely.
Boy Scout Rule: Leave the code cleaner than you found it—only clean up the code you touch, don't refactor unrelated parts just because it's convenient.
Test first: Translate tasks into verifiable goals—"fix a bug" → first write a reproduction test, then make it pass. It's only done when it runs successfully; "it should be fine" is not a conclusion.