Another one that my dad and I have used is to take a medium sized treble hook, and then gently put it under their jaw, then a slight jerk upwards, and you have your frog. If you're using a gig, do it at night, their eyes give off a slight glow when the light hits them. You can sneak up really close as long as you keep the light between you and the frog, and try walk softly...they can feel the ground vibrate.
~~~Cattleskinner