There are a lot of threads about how to combat snails. Just enter the word in the search box at the top of most pages on the forum, and you'll find a ton of suggestions.
My personal preference is to go out at night with a flashlight and hand pick the critters. Then I drop them on the ground and step on them. Do this faithfully for one entire season -- spring, summer and fall -- and you will get the problem under control. At least that has worked for me. I still go out snail hunting about 3 nights a week, but none of my plants suffered much in the way of damage this year. Most of the snails I've found have been tiny, about 1/4 inch in diameter, not like the 1 1/4-inch monsters I was finding last year.
Snails are hermaphrodites, but can also mate in the usual manner. Either way, they lay viable eggs about 6 times a year. Every snail you kill today means as many as 2400 that won't be around to munch on your plants next year.
I know that ducks love to gobble up snails, so if you're in an area where you can keep ducks, you might want to try that.
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams