Preheat your skillet over medium to medium-high heat. When fully heated, add 1 tbsp of high smoke point oil (canola, avocado, peanut oil, ghee etc) and heat the oil for 30 seconds or until shimmering.
Dry the salmon fillets completely. Moisture is the enemy to crispy skin if cooking skin-on. Pat dry with paper towels regardless of cooking skin on or off. Season the skin with salt and pepper. Season the flesh as you desire.
Using fish spatula or another flexible spatula, press the fish in the pan, skin side down for 30-40 seconds. Much like when searing a steak, do not be tempted to flip the salmon prior to it being cooked enough. The drier that skin is going into the pan, the crispier the skin will be. Fish skin shrinks when it cooks so adding pressure will keep it flat and covering the flesh.
When skin is crisped and easily releases from the pan, flip the salmon over and cook an additional minute.
Remove fish from pan when it reaches 125°F (medium-rare) and let rest for 5 minutes. Serve skin side up. I like to use this time to make a pan sauce if desired.