The pre-open checklist I run every single morning
Six things, takes about ten minutes:
1) Broker connected and account balance matches what I expect.
2) Yesterday's positions actually closed. No surprises.
3) Strategy is the one I think it is (I have mislabeled versions before).
4) Daily loss limit set. Not "I'll watch it."
5) Universe list looks sane — if it's full of names I've never heard of, something is off upstream.
6) Phone alerts working.
If any line fails I don't start. Sitting out one session has never cost me as much as starting on a broken setup.