The key to avoiding salmon sticking to your pan is to preheat it very well before adding the salmon. Dry the salmon off before adding on the salt and pepper as moisture can cool down the cooking surface and cause sticking. The salmon filets should sizzle when you place it in the hot oil. Then do not touch it at all. If you try to flip it too soon it will not release from the pan. Use a very thin fish spatula and make sure to wiggle it between the hot cooking surface and the salmon. If it is stuck, let it sit for a minute longer and try again. If your pan is good and hot it should release without any sticking. Then you'll know it is time to flip it.