Slugs have been eating my hostas for years! I have learned two things that work to keep the slugs at bay: place small pie tins (I use disposable pot-pie sized) around and throughout the hostas and pour about a 1/2 inch of beer in each one. The beer entices the slugs into the beer and they can't get out again, they cannot burp either, they die from the fizzle in the beer. We have also taken copper scrubbers and cut them into small pieces and sprinkled them throughout the garden. For some reason slugs hate copper and won't cross it. However, if they're already in your garden, they will be able to avoid a surround of copper, That is why I use a copper scrubber and cut it into tiny pieces and sprinkle the pieces all throughout the hostas, try to make sure you surround each plant. Slugs do not like salt either. But I've never used it in my gardens because I have no idea what salt will do to my garden.
I have read more and found that plants love Epsom salts, especially tomatoes and if a delicate plant like tomatoes like Epsom salt, I can't imagine it would hurt to sprinkle it all around the hostas - I can't kill my hostas if I try!
Linda's ideas are good ones. You can also try diatomaceous earth (make sure you get the garden kind, not the swimming pool kind) or a bait product called Sluggo, which is organic. They both have to be reapplied after a rain.
coffee grounds and crushed eggshells around your plants
Slugs do not like copper. You may want to place a few pennies in the area or make a garden ball covered in pennies.
BEER!!!! They love it!! Just pour a little of the magic beverage in a saucer, set it in your troubled area and GUARENTEEEEED, they will go to the party, and never come out!!