Even though you may not like the process – handpicking is an excellent way to start controlling snails and slugs. I was able to reduce the snail population by 85-90% (my estimate) by going on “snail patrol” at night. A flashlight and an empty milk carton are all that is needed. You might want to wear gloves if you are squeamish. Once the carton is full, you staple it shut and place it in the trash can. Have the kids earn their allowance by offering a “bounty” per snail, is another idea.
Snails and slugs like to hide in dark, damp places. Place boards on the ground, so there is about one inch of space underneath. Check these boards daily and kill the wildlife that has collected there.
Barriers can also be useful if you have trees with single stems. Citrus and avocado, especially, can be pruned so that no limbs touch the ground. Then place a copper foil wrap around the trunk. These wraps and use instructions are available at most garden and hardware stores. Snails and slugs will not cross the copper band.
Baits are also useful. There are many formulations, some can be sprayed on plants for protection. Others are applied to the soil and can be used to ring and protect a given plant or group of plants, or the bait can be placed as a barrier between the place where the snails/slugs hide and the plants on which they are feeding. Baits should be refreshed every week or so, so the bait barrier does not lose its effectiveness.
Finally, drip irrigation is a great way to keep plants irrigated, but keep plant foliage and the soil surface dry and make the garden habitat unfavorable for slugs and snails.