A would-be small animal trapper has many choices. Three simple ones are a box with a one-way flap, a hole and a snare. For the box, put bait inside and have the flap open inward but not outward. A hole can be covered with a board balanced on a pivot stick. And a snare can be placed above the animal's hole. Designs for more complex traps are available online.
The simplest way to trap a small animal is with a cardboard box. Take a cardboard box and cut a flap in the side at ground or floor level. Cut the bottom, one side and the top of the flap, leaving it still attached on the other side as a hinge. Push the flap inward slightly and stick a piece of toothpick or twig into the edge of the cardboard flap away from the hinge so it cannot be pushed back outward. Put the box on the floor or ground with bait inside. Do not repeatedly bend the flap, or it can weaken the hinge.
Dig a hole with sides as slippery as possible. Put a smooth stick or rod centered across the top of the hole. Cut a piece of cardboard with an area slightly less than opening of the hole. Tape or fasten the cardboard onto the stick so the cardboard is flat and balanced, almost covering the hole opening.
Put bait on the center of the cardboard over the stick so it will not unbalance the cardboard. When the animal walks onto the cardboard for the bait, it will flip over and drop the creature into the hole.
Tie a piece of string or fishing line into a slip knot, such as a lasso. Tie the non-loop end to a stick firmly stuck in the ground. Put the loop around the hole of the animal to be trapped, making the loop slightly smaller than the body of the creature. When the animal tries to pass through the loop, it will snag on the snare. The snare will tighten as the animal tries to pull through, trapping it.