First get the fish boat side! If you use a net, leave the fish in the net and preferably in the water. If the shank of the hook is showing at the mouth of the fish, use a grasping type hook removal tool or long nose pliers to grasp the shank. Use the weight of the fish as leverage and quickly push the hook away from the direction of penetration. With small fish and no net, handle the fish as little as possible, and remove the hook by hand. Hard-tailed fish, like the mackerel and tuna family can be handled best by the tail. Allow the fish to rest and recuperate in the water either by holding the tail or leaving it in the net for a couple of minutes. For fish that come up from deep water with their air bladder in their throat, take along a hypodermic type needle to insert in the bladder to relief the pressure in the bladder before releasing. Only bring a fish completely in the boat if you plan to keep it. Some useful tips would be to use circle hooks whenever possible, because they help prevent swallowed baits and gut hooks. If a fish is gut hooked, just cut the leader or line as close to the hook as possible and then release the fish. Acids in the body of the fish will dissolve the hook literally within days. NEVER gaff a fish you plan to release. Open wounds from a gaff invite infection and draw predators. found this info and am passing it on.