If you're grilling fillets under an inch thick, you are likely to get the best results by abstaining from flipping. There is so much hand-wringing when it comes to turning fish over on the grill that I was relieved to hear, try, and succeed with this piece of advice.
If the skin is on, simply oil and season the fish, oil the grill, and lay the fish over medium-high heat with the skin side down. Close the lid to ensure the fish is cooked through. Remove with a broad, flat spatula after anywhere from 2 1/2 to 5 minutes, depending on the thickness of the fillet.
After removing the fish from the grill, allow it to sit for a few minutes and finish cooking at its center. When all is said and done, you want an opaque appearance with an internal temperature of 140 F degrees.
Have you tried grilling fish on one side only? What are some other fish-grilling tips you can share with us?