Before placing the fish on the grill, season it to help prevent sticking. Take a wad of paper towels and dip them in vegetable oil. Using tongs, rub the oiled paper towel wad on the grill grates to season them. Then, place the fish on the grill (still over high heat) and cook on each side for 7-8 minutes. If you have very large trout, you may want to cook for longer, until the flesh of the fish is cooked through. You can also grill the two halved lemons, cut side down, and removed from the grill once they begin to char. These roasted lemons are both beautiful to serve alongside the fish and have a delicious flavor when squeezed on the fish.