Traps.
The mousetrap is one of the oldest and most effective household products ever invented. It has changed little with centuries of use. Buy traps designed for the type of rodent you have and bait with cheese or raw meat. Rat traps can be baited with raw or cooked meat, fish or strong smelling cheese. Adding a few drops of fish oil from your fishing tackle department, will make the bait even more attractive. Another effective mouse bait is to mix powdered milk with water to a thick paste and fill the trap using a putty knife. Put the traps down where you have seen the rodents run, or near a known hole. Leave them out each night until you catch no more rodents. Avoid putting the trap where it could tumble into a crevice or between walls when sprung.

Baits.
A number of commercially prepared baits are available to catch rats and mice. Some are water resistant and suitable for outside use, others some in solid form to drop into hard to reach places. Generally, for mice you need small amounts of bait in several locations. Rats require large quantities of bait in one or two locations. You should continue to put bait down until it remains uneaten.

NB. Be very careful to place traps and baits where children and pets cannot get at them.

Prevention.
Prevent mice and rats getting into your house by checking regularly for holes. Mice can get into quite small crevices. Cover any obvious holes with aluminium flashing or flattened tin can lids. Mice cannot chew through steel wool so use pads of steel wool to plug their holes. Put poison into holes or cracks before you seal them up. Mice and rats can eat through wood and other materials so any suspect holes around built in furniture under doors etc should be sealed, first putting poison into the hole.

Tying your bait to the trap ensures the victim won't "escape with the bacon". Never leave where innocent animals may be attracted to it and injured or killed.

For exposed situations such as in hen runs, place the bait in an old piece of pipe. This will allow the mice and rats in, and keep the hens out.