one thing to do is go out at night with a torch and just pluck them. another is to put crushed seashells(u can get in garden center) around slugs and snails cant go over them, salt will damage ur soil so dontpour that on them. if u catch them at night put themin a jar and feed them to ducks and moorhens at ur local park or pond the love them.
hope this helps.
peace and good growing, from FTF