Sluggo, Es-car-go, and Safer's Slug & Snail Bait seem to all work well, per our staff entomologist. All are made from iron phosphate have been found to decrease slug populations without harming birds, small pets or humans. I think if you type in a search for any of these products you'll be able to buy them online. Good luck!!
I've used it successfully. It works best if you dig a little place and put the container so that the slugs can go in at ground level rather than climbing up. A deep jar top even will work. Put it out in the evening and be prepared to discard the slimy little bodies in the morning. You can drink half a bottle of beer and let the slugs drink and drown in the other half - sounds like a good deal, now doesn't it?
Beer does work really well. You can even use the cheap brands, they aren't picky!!! Do discard it in the morning,once the snails fall in they drown. I use disposable cups clean-up isn't that bad.
We've had excellent results after adding predatory snails to our yard several years ago. 'Rumina Decollata' snails are tiny, cone shaped snails that eat common yard snails. The 'Rumina Decollata' snails burrow into the soil. We see them only after a good rain.