Here is a method I have not tried yet but apparently works well - must be done early in spring I guess.
"The key is doing it before the slug eggs have hatched. Ken Beattie from the Get Growing TV program explained that the eggs are laid in the ground, usually along the edges of sidewalks, walls, etc. He also said the solution does not harm plants. I agree have found this to be true.
I use a mixture of 1 part ammonia to 10 parts water. I use a watering can with a small downward pointing spout and pour some along the edges of all sidewalks, retaining walls, the deck, anywhere the ground or lawn meets a hard surface. I do not drench the whole yard nor do I water entire flowerbeds, just the edges. Two watering cans of this mixture does my whole back yard. I especially concentrate on the shady areas of the yard where I used to see slugs or their trails, I do not bother with the sunny front yard as I have never seen evidence of slugs there.
No, I would not water directly on my hostas. nor do I water the soil around plants with this mixture. In fact the hostas aren't even up yet, when I do the first application, which I did 3 to 4 weeks ago. I did the 2nd application yesterday. That should be it for this season."
Not being averse to using the occasional chemical I sprinkle slug bait around the hostas and put pieces of cedar shingles over. Easy enough to scrape dead slugs off the shingles and they are hidden by the hosta growth. Also animals cant ingest. I used to have beds marked off in my veggie garden with old fence boards and I could go out in the morning and scrpe them off the underside of the boards. My Mom used to put out the letover skins of the grapefruit my Dad ate every morning! Pick em up and throw away next day!