You'll know it's ready to flip once it releases from the pan.
That grip is the crust still forming, so don't nudge it around if it's not releasing. The protein will almost always tell you when it's ready.
The release and the browning are the same event
That's the part worth knowing, and it's what turns the protein will tell you from a rule of thumb into something you can rely on.
When protein meets hot metal, the surface proteins bond to the pan, chemically and by gripping into the microscopic pits in its surface. Browning then consumes the very amino groups doing the holding, and the drying surface pulls in on itself, so the pan lets go because the crust has formed. The meat lifting freely is the crust reporting itself.
Pry a steak up early and it tears, leaves its crust stuck to the pan, and starts again on a surface that's now wet. Waiting isn't patience for its own sake. It's waiting for a reaction to finish.
How much browning you want depends on the protein. The signal is the same either way.
Where this doesn't hold
- Nonstick. Nothing sticks, so nothing releases. A cook waiting for a signal that never comes will overcook the piece.
- Anything you're told to keep moving. Ground meat broken up as it browns, cubes rolled to colour all sides. Those steps say to move it, and they mean it.
- Anything that's not a protein. Polenta, halloumi and mushrooms sear and release on their own schedule.
Two rules that travel with it
On a steak seared hard, salt goes on early and pepper goes on at the end. Pepper burns before the crust has formed. The variable is the heat, not the meat, so this is a steak rule and not a general one.
On a multi-round sear, wipe and re-oil the pan between every round. The bits from the last round will burn and turn bitter into the crust.
And what comes after the sear is the rest. Rest it for as long as it cooked, and on a multi-round sear, as long as the last round.