Sink the pans into the ground so the lip is at ground level. Empty the pans at least twice a week. Use diatomaceous earth. Diatomaceous earth, sold as Perma-Guard, is made from the ground skeletons of small fossilized animals. It has many sharp edges which lacerate the bodies of slugs, causing them to dehydrate and die.
Diatomaceous earth is non-toxic.
Use chemical pesticides. Granules or baits containing metaldehyde are effective in controlling slugs but need to be used with caution. They cannot be used on vegetables and should not be used where children or pets may pick them up or eat them. Placing the bait in a partially flattened tin can will limit the access children and pets have to the bait.