Crayfish are some of the coolest little critters you will ever find in your neighborhood ponds or creeks, and they are a great way to get kids up and out of the house, possibly even excited about the outdoors! Personally I have never attempted to catch crayfish for food (although I do enjoy eating them), but catching them for fun can be a fantastic introduction to pond ecosystems (for kids) or just a good way to waste an afternoon.

Crayfish live in all sorts of freshwater environments, but prefer areas with shelter as they are largely nocturnal creatures and rather skittish as well.  An area with clear water, some reeds (crayfish love grasses for shelter), rocks, logs, other organic matter lodged in the bottom of the water source will be a good place to find crayfish.  A good rule of thumb early in the summer is if you find tadpoles there, chances are there are crayfish if there is adequate cover for them.

When startled, crayfish will whip their tails underneath them and shoot backwards in the water.  If you happen to stumble across one on the banks of the water source, it will have the same response only the result will be splashing you with water and making a somewhat startling clicking sound.  Therefore if you are trying to catch a crayfish that is in the water, position your net (hands, whatever) behind the creature and attempt to startle it.  Anticipate being pinched.  If you happen to find a crayfish on land, your job will be much easier and you can just pick it up directly. 

The best place to grab a crayfish is on the smooth part of thorax (called the carapace) directly behind where the claws attach to its body.  If you grab here, the crayfish can wave its claws at you all it wants but will not be able to pinch you if you keep your hand behind its claws.

If you feel the need to set up a trap to catch these guys, something simple should suffice.  A bucket weighted to the bottom of the shallow part of a pond with a rock would do nicely.  Add some form of shelter for the crayfish to use, put some sort of fish/meat into the bucket (opinions differ on this- crayfish can be caught with anything from cat food to hot dogs, but they normally eat fish so start with that).  Leave the bucket overnight, and the next day you can stop by, pull the bucket up by the handle and see what you've caught!

If you successfully catch crayfish and want to keep them as pets for a few days, use water from the pond you caught them in to fill the aquarium/tank they will be inhabiting.  If you do not have a bubbler for the tank, you should replace the water everyday or every other day to prevent the oxygen in the water becoming too depleted.  You can feed them almost anything, they are scavengers by nature.  They will eat vegetable matter, fish food, algae pellets, cat food, hot dogs, etc. etc.  This point is only valid if you are planning on keeping them short term though, since the health of the animals should be considered in what you feed them if they are being kept long term.

As a side note, I do not recommend keeping wild crayfish as pets long term.  It is a more valuable lesson for children to learn to enjoy nature and to give back to it than it is to keep the crayfish to the detriment of their health to prevent children from having to experience loss.  Even young children can understand that animals want to go home just like they do, and you can turn even the unhappy moment of letting a novel pet go into a learning experience.  Crayfish are sometimes sold at pet stores, these are more viable options for long term pets.  DO NOT, however, EVER release pet store bought fish/crayfish/animals into the wild, they can damage the local flora and fauna of an area and will likely die a slow unpleasant death in an unfamiliar environment.

At the end of your stint housing your crayfish, return them to the pond you found them in.  You can plan visits to go see them from time to time.