Put a lump of yeast or sprinkle powdered yeast into a jar of warm water and sugar. The jar should be big and deep enough from keeping the snails and slugs from crawling out. There are containers available at the garden store specifically for this purpose.
Dig a hole in your background, deep enough for the jar to sit upright. Preferably near to the plants, where the slugs and snails are more.
Repeat this activity at every few feet. Dig holes, and place these jars throughout your garden, at a distance of 6 to 8 feet from each other.
Check these jars daily and remove any slugs and snail that have been attracted to the jars. They would have crawled in to the jar and drowned. You can take them out and put them in the compost pile or leave them in the garden to decompose and add to the organic matter of the soil.
Renew the mixture in the jar regularly. As rain and evaporation will have negative effects on the mixture and stop it from working. Keep it fresh!!