When the hosta "eyes" appear, mix one part household ammonia with ten parts of water and pour this mixture around the eyes close to the plant. It doesn't hurt the plants, but it does dissolve the eggs that are laid around the roots.
Save eggshells & coffee grounds & sprinkle them around hydrangeas & roses. The calcium is good for the roses & the coffee grounds make the soil more acidic for the hydrangeas. Organic Gardening - How to Deter Slugs and Snails With Eggshells
This guide is about keeping slugs off hostas. Slugs are a common pest to Hostas and can munch large holes in their leaves. To protect your hostas, especially those growing in pots, cover the soil with used coffee grounds. Not a slug in sight!