The challenges when grilling fish are twofold. Your first intent is to sear the fish so that you achieve a crispy outside while ensuring that the fish wil be cooked all the way through. The end goal? A nicely charred exterior that envelops the smooth and luscious texture of the fish.
Fish such as tuna, salmon, halibut and swordfish, whose texture is more like beef or pork, should be grilled directly on the grate. More delicate fish such as tilapia, sole and flounder, sometimes fare better when grilled in a foil packet or grill basket.
Grill with confidence:
Your second challenge, and perhaps the trickiest, is figuring out how to keep the fish from stick to the girll - every fish flipper's nightmare.
The solution is a well-prepped grill, dry product, and the proper level of grill heat, which is usually medium-high.
Prep the fish:
Wrap the fish in paper towels or a kitchen towel, to get rid of excess moisture, and place on a large plate in the fridge until your grill is ready. If this fish is wet, it will steam, not sear.
Prep the grill:
Turn the heat on the grill to high and get ready to prep the grill grate. You'll want to ensure first and foremost that your grill grate is as clean as posisble. As you're heating up the grill, cover the grate loosely with aluminum foil. The intense heat will cause any debris to break down and dissolve. This also minimises sticking. At its highest heat, this should only take about 10-15 minutes.
Brush the grill grate until clean:
Remove the aluminum foil from the grate. Using a stiff-wired grilled brush, scrape the grate clean. Fold a couple of sheets of paper towel into a small square or pad. Grasping the paper towels with tongs, dip the paper towels in oil, then rub over the bars of the grate. Continue to wipe the grate with the oiled paper towels until the grate is somewhat glossy. Plan on doing this about five times. It's a good idea to re-dip the towels in oil for each application.
Season the fish properly:
Remove the fish from the fridge and lightly brush both sides with oil. Season simply with salt and pepper. Position the fish skin-side down diagonally on the grate. This not only creates those masterful grill marks you see in restaurants, it actually makes it easier to flip too.
Leave it alone:
Reduce the heat to medium, cover the grill and let cook! Don't try to move the ish until you see that the skin side has a nice sear and looks crisp. If you're not sure when to check the fish, try gently lifting with a fine edged spatula after a few minutes. If it doesn't lift off easily, let it cook a bit longer and check at 20-second intervals.
How to flip:
Using two fine-edged spatulas, lift the fish fillet underneath from both sides and flip the fish. Then cover and cook until the fish has reached the desired doneness. If you don't have two spatulas handy, try using a fork. When cooked properly, the meat will be firm to touch, flake easily with a forker and appear opaque all the way through.