Start by choosing a type of trap. It's best to avoid live-catch traps, because disposal is tricky. Ground squirrels are considered pests, and it's illegal to release them at another location. The best bet is to choose between a box trap or tunnel trap.
Place the trap on the ground near a squirrel burrow or runway to improve the chance of the squirrel seeing and responding to the bait. Then set up the trap by placing the bait, such as barley, oats, walnuts or almonds, behind the trigger. Let the squirrels become comfortable around the trap before setting the trigger.
Place the trap in a covered box in order to reduce the danger to pets or children. This is especially important in order to prevent endangered non-target wildlife, such as kit foxes and burrowing owls, from trying to take the bait. Leave a small entrance in the box about 3 inches wide.
After the trap is set, check it at least once a day. Remove the dead squirrels immediately. When disposing of them, wear protective gear to prevent diseases.