Before you even think about catching and keeping one of these behemoths, check your state law. In many places it is illegal to keep a snapping turtle is a pet. Oddly you can kill them in those same places, but keeping them alive is considered a bad thing for some odd reason. If this isn't an issue in your area, read on.
Catching
Snapping turtles can be a little tricky to find. They are most common in eastern united states, though they are scattered in other places. They are aquatic turtles and can be found in most lakes and rivers. The closer you re to shore, the smaller they seem to be. Despite their reputation, snappers would much rather avoid a fight while in the water, so this is the ideal place to get them. If you come across them on land, BEWARE! They will earn their name by trying to take a bite out of you. They are slow moving and fleshy turtles, and they try to protect themselves by scaring you away since they can't run or hide out in the open. As with most turtle species, even if it is legal to catch one in your state, you can't keep one under four inches long (shell size) so keep this in mind when finding one of these feisty little guys. When you do find one, be very careful how you handle him. Many people like to pick them up by their tails. DON'T DO THIS! It puts a lot of strain on the animal's spine and they are not light creatures. Either grab him on the sides, or if he is trying to scratch you, put one hand on his belly while holding him still with the other on his back or gently gripping his tail. Whenever handling a snapping turtle, I strongly recommend wearing protective work gloves. They bite very hard and scratch with long, sharp claws.
Housing
Snapping turtles can live in the foulest water around, but that doesn't make it a good idea to keep them in it. Like most turtles, an aquarium will do for the smaller specimens, but keep in mind that these fellas grow to be over two feet long, and that's just the shell. In time you will want to move them to an outside pond of some sort. You can also modify a kiddy swimming pool to suit them, but this is very hard and takes up the better part of a room. If you cannot accommodate a full grown snapping turtle, I recommend you don't try to keep one as a pet. Snapping turtles hunt near the bottom of lakes and rivers, waiting in the mud for fish to come along, but they will come up to the surface to feed, so deeper water is fine.
Cleaning
If you have a smaller snapping turtle, a normal filter designed for turtle tanks should work just fine. If you have a larger pet which needs a kiddy pool, you will need to change the water out at least once a week, or every other day if you feed him meat because it can start to smell foul very quickly. If you have an outdoor pond large enough to accommodate an adult, you don't need to worry about cleaning it. But I would recommend putting up some kind of fence as snappers aren't shy about crawling over land long distances to get to new water sources.
Feeding
Snapping turtles will eat just about anything you give them. They have been known to crawl onto land to feed on carcasses of large mammals, and floating chunks of meat in the water. They even attack fish caught by fishermen. And yes, they will eat commercial turtle pellets as well, but when they get older it's hard to feed them enough of these. I recommend feeding larger turtles large minnows. It will be messy, but fish is a normal part of their diet. It is also expensive, so keep this in mind before deciding to keep a snapper.
Handling
I really can't recommend handling a snapping turtle unless you have to. They don't get used to you and they will try to bite you from the day you catch them to the day they die/you let them go. Snapping turtles have incredibly strong jaws. I've seen them bit through sticks as thick as a broom handle with ease. It wouldn't be hard for them to take off a finger. They also have very long necks which can snake out and get you by surprise. Keep your hands well away from their front. Always wear protective gloves and always wash your hands after handling it.
Friends
Snapping turtles are loners by nature and don't like members of their own kind. In fact, they don't like anyone. Anything you put in with them will probably be eaten. The only time snappers tolerate each other is during mating season.
Fun Facts
Snapping turtles have a “lure” on their tongue that looks like a worm. They wait on the bottom of a pond with their mouth open and wiggle their tongue until a fish comes close enough for them to eat. Snappers generally don't like direct sunlight because they spend most of their life at the bottom of lakes where it is dark.
