Amphibians and reptiles
Frogs, skinks, geckos, monitor lizards or similar, and turtles are relatively easy to catch. Frogs and toads deserve a certain caution. Stay away from any brightly colored frogs - anything with contrasting reds, yellows, blacks and so on. Many species advertise the fact they are toxic by color. A notable member of this group is the poison arrow frog. Rubbing an arrowhead on its back picks up poison to take down a bird. Avoid toads. Generally, but not always, these have warty skin which usually contain toxin glands. Cane toads for example have toxin glands on its skin. Ingestion can kill birds, snakes, mammals. It's best not to tempt fate. Warning! Cane toad tadpoles are small, black, usually in large schools in shallow pools. DO NOT DRINK FROM THESE POOLS! The tadpoles, like the adults, are toxic. This leaches into the water. Salamanders and newts are also amphibians, and easy to catch. To my knowledge they are all edible.
Small reptiles such as skinks and geckos are highly overlooked as food sources. Geckos can be caught by hand. Skinks are a bit trickier. One way of catching them is by a pitfall trap. Dig a tin-can sized hole, place aforesaid can into the hole with some sort of bait such as a bit of sugar with some water poured into the bottom. As an aside, this is used by zoologists to sample lizard densities. It works. Place some stones and vegetation in the bottom to protect whatever falls in from rats. Placing a flat rock as a cover for the trap is a good idea. Lizards like basking on warm stones, but they also like hiding under them. Straight into your hole. In the absence of a tin can, simply digging a hole with bait and vegetation will work. Yeah, the buggers can climb out, but if it's nice enough down there, they don't know they're caught until you scoop them out. If you are using a solar still, these are good places to incidentally trap lizards and insects.
Bigger lizards such as monitors or iguanas can be caught with big pitfall traps baited with offal, or with less subtle approaches. A suitably heavy club used with extreme violence can stun, then despatch the animal. Don't be squeamish. Remember that the bigger the animal, the stronger the bite. Monitor lizards have nasty teeth that will scrape you raw leaving behind an incredibly nasty infection. Don't take chances, make sure it's well and truly dead. After stunning, grab the tail to lift the rear legs and keep clubbing. In case you think I have some sadistic streak about me - I don't. I just get it over and done with as quick and painlessly as possible. Two species of lizard to note are the Gila monster and bearded lizard in southern USA, Mexico, and central America. These are chubby, tasty looking lizards that have a venomous bite. They are edible however. I have no personal experience with them. A basic principle applies, as with dealing with all animals - Don't get bitten. Monitors (and turtles for that matter) can be caught by nooses if you have offal as bait, and they can also be caught in baited twitch-up traps (see Mammals). The noose as pictured is good for medium sized things that can bite. Like dog-control nooses they keep the animal away from you. However for bigger animals such as crocodiles (below) they should be modified.
Turtles, alligators, crocodiles can also be stalked, jumped on, and captured. Previous rule applies - don't get bitten! Turtles can take a finger off. Be VERY careful in crocodile country. I have caught crocodiles before, but only on my own terms.
Don't blithely wade into their territory. You probably won't even see them until they drag you into the water from the edge. For those of you interested, first use a modified noose to the one above. Tape a noose to the end of the stick as above, but have a long rope feeding back. I kind of loop it along the stick, with the rope tail end away from my body and the action. BE INCREDIBLY AWARE of potential entanglement. The croc will generally break the stick if you just have a noose on the end, because they are bloody strong and they do a death roll. You will feel a bit silly just holding a broken stick when face to face with a P.O.'d croc. After noosing around the top jaw (the blighters often have their mouths open unless they are about to bolt away); pull tight and haul the rope as it ties itself up rolling around; Launch yourself onto its back from the blunt end, and make your way up the back to the pointy end; Hold the jaws shut and tape the jaw shut; Cable tie or tape its front legs, then back legs behind its back. All done. For one person by themselves, I would stick to an animal <2m total length. After this length they start to bulk up a bit, and it's best to have 2 people. Just out of interest, the largest I've caught was 2.5m. There were three people for that one, we could have done it with two.
Snakes taste good. With the exception of Australia, on balance most of the species you will encounter are harmless or not-so-bad. Keep your distance, and use a club. I would suggest having a club in one hand, and a stout, leafy branch in the other. I use the adjective stout for a good reason. In the excitement there is a tendency to grind the stick hard into the ground a wee bit hard. There's nothing worse than being left with a tail in one hand, a broken stick in the other, and nothing between you and the head of a very P.O.'d snake wondering who's holding its tail. Don't go for the Hollywood-style forked stick approach - it requires quite a bit of skill and practice. A stout branch with lots of forking leafy bits has more chance of holding, distracting, reassuring the snake until you can hit it repeatedly and violently until it is not moving. Then... secure it by the tail with one hand, holding the head down with the branch and make your way up with the other hand to the pointy end. Cut about 15cm/6 inches behind the head to make sure you miss any venom glands - just saw the head off. Don't be subtle. Oh, and yes - it is possible to get bitten by a decapitated snake head as the nerves go through their final firing. Take selfies at your own risk.
This all sounds very gung ho - it is up to you to make a risk assessment. I am happy catching a lot of snakes, but I am not going to take on a 2m taipan or brown snake. I've seen how fast they can strike. However a 1m death adder (nearly as venomous) could be reasonably easily dispatched with a 1.5m club. If in doubt, don't do it.
Preparation and cooking
To my knowledge reptiles are relatively free from internal parasites. I generally cook by roasting in the skins. Simply gut the animal, spread the gut cavity out with some sticks to make sure it cooks through, and place on the coals of a fire. This is the way Australian aboriginals cook goannas (monitors). I'm not sure if the guts are particularly good or worth eating - I mistrust offal generally because if there are parasites, that's where they'll be. Offal, however, makes good bait for other animals.