I fish frogs, A LOT! One of the first issues I had with frogging was poor hookset. I actually saw a bass throw a frog that was deep in his throat. Knowing that the frog was deep in his throat and still came out, I figured it was poor hooksets. I quit using the medium rod and went to a much stiffer medium/heavy-fast rod and problems solved. I quickly noticed that most of my hooks were coming straight up into the fishes head and nose, making it hard for the hook to get good penetration, but with the stiffer rod, the hook was able to cleanly break through the barrier when before the rod was too weak.
Also, frogs either get their legs ripped off, or they get swallowed WHOLE and are engulfed. I've found that when the legs get hit, if you give the fish a second or two, they will re-gulp and then swallow the entire frog. If the frog is swallowed whole, its rarely spit out quickly. So either way, as soon as you see the bulge take your frog, count to two in your head, then yank the hiney-hole out of that fish. The good thing about frogs, if the fish misses, often times they will hit it again on the next cast.