Salt on the skin helps draw out any moisture resulting in crispier skin.
Fish fillets should ideally be pan-fried with skin on when possible, as it helps keep the fillet together. You can remove the skin prior to serving or eating if you prefer.
Don't overcrowd the pan. The temperature will drop quickly, making your fish sweat rather than sear.
To avoid the risk of your fish fillets breaking up, only turn once.