In addition to these natural traps, there are any number of traps you can fashion. We have found grapefruit halves, placed cut-side down, and overturned, unglazed clay pots to be attractive to slugs and snails. If you use clay pots, you will find that a crushed snail or two left inside will act as an attractant to others as it decays. Place overturned pots on the shady side of plants so the pots stay cool in the daytime, and leave the ground uneven so snails can find entrance under the rims. Wooden boards or asphalt shingles, kept cool with aluminum foil placed on their top side to reflect the sun, and elevated from the ground with a pebble, also work.
Beer is a well-known attractant for slugs and snails because of the yeast it contains.
Commercial yeast mixed with water can be used to the same effect. The trick is to exclude pets and other larger animals from the sudsy trap. Garden writer Gene Logsdon describes an ingenious beer-baited pit trap made from a large coffee can. The entrance is a rectangular opening cut one third of the way down the side of the can. The can is sunk into the ground to the level of the opening.