Getting rid of them...there are several organic methods. Fill the lid of a mayonaise jar with beer--I've heard the snails will crawl in and drown. Sprinkle them with table salt and they'll dissolve into a milky goo right before your eyes. I've also read to place a wide board on the ground and they'll gather beneath it for shade & moisture. Lift the board and dispose of the ones you find.

My own preferred method (so far) is to save egg shells and in spring just sprinkle the crushed eggshells around my plants. Snails won't crawl across the shells because it'll cut them. Diatomaceous earth works on a similar theory but I've never tried it. A friend gave me three bars of Fels naphtha soap and suggested I cut it into cubes and set them near my plants in spring to discourage snails. I haven't tried it yet so can't vouch for its effectiveness.

The other methods of control mentioned by garden weed are tried and true....though I can't imagine why Fels Naptha would repel them, lol.

There are organic approved slug/snail baits with the active ingredient iron phosphate that are very effective in killing these creatures, if you find that the population is abundant. In the meantime, I would simply collect and dispose of any that you find or set out a few beer traps.

Anything that will reduce slug populations in gardens will work for snails.

So before you annihilate, I suggest you take a sample (secured in a clear, rigid container) to your county's Extension Service office.

Find it using this map
http://www.csrees.usda.gov/Extension/