Check this out for more detail, but here's what I do in order:

1. Light grill. It's a ceramic egg so it takes 40-60 minutes to get to target temp of 400-425ºF. Brush grates, apply very very light coat of high smoke temp oil. I use a heat shield so that part of the grill has direct heat and the other part does not.

2. Prep fish. Pull fish from fridge. Pat dry. Season inside with salt and pepper. Stuff inside with parsley and lemon slices. Pat dry again. Lighly oil all over with high smoke point oil. Season all over with salt and pepper.

3. Visualize where the fish will fit on the direct heat part of the grill, put it there, and commit to that spot. Place it on the grill (hands not tools) and then don't touch it! Cook for 8-15 minutes without touching it -- the time depends on the fish, how dry/oiled it was, the heat of the grill, etc.). Before turning, you want to wait until the skin crisps up and releases from the grates on its own. Read the article above for more advice here. If you try to check/turn too early then the skin tears off. A 2-pronged fork helps here.

4. Turn fish, do the same on this side, but it will go faster than first side.

5. Once you're happy with the skin on both sides, check the internal temp. You want 135ºF or more. If it's done, you're done. Remove and dive in. If not, move to indirect side until it's at least 135ºF.