Whether you want frogs for fishin' or eatin', my favorite way to get them is to shine a spotlight in their eyes, then snach 'em quickly with your hands. Make sure to keep the light right on them not giving them darkness one moment, or they'll be gone. Keep 'em wet by putting them in a closable mesh bag and dipping it in water momentarily. Another way is to knock them unconcious with a limber stick or crappie rod (inhumane, I know...don't slaughter me over it). Or if you only want bullfrogs, dangle a crappie lure in front of them with your fishing line. They'll bite it and you'll have 'em hooked like a fish. The leapord frogs good for bait can't seem to fit the whole thing in their mouth. Anyway, hope that helps, although it's not a trap.
Another way is to get out in a private pond with a .22
Make sure u have high velocity rounds, shine a spotlight on the frogs and SHOOT UNDER THEM.
This stuns the frog and you can then go pick it up. The come back to life in a couple minutes. We use small flat bottom boat for this since you can cover more water than wading and is alot cleaner.
Sometimes it kills the frogs but leapard frog legs taste good too, just not much meat on them.