What is the best way to find all the frogs in Metal Gear Solid 3?

Use the audio amplifier thing. and wear the uniform with the ducks. i think its called the GA-KO uniform. It makes the frogs croak. Use the amplifier to pinpoint on where they are. The Official Stratergy Guide has a whole section dedicated to this, each section of the game has a map, and even a screen shot of the kerotan frogs. This is how I found them all. [Plus the gako camo helps to sniff 'em out.