For a persistent problem, use an insecticide soap. Spray infested leaves with soapy spray, then rinse off with clean water after the soap solution has dried. Test on a few leaves before treating the whole plant. Slugs will be drawn to the beer and crawl in. Replace beer frequently.
Commercial traps are also available.
If you have raised beds, try tacking copper strips or placing pennies on the outer frame as a barrier. Slugs will not cross over the copper. Remember to remove slugs from within the barrier. Compost can be made from grass clippings, yard prunings, wood shavings, or dead leaves. Use natural soil amendments like blood meal, fish meal, fish emulsion, kelp meal, manure and compost to help supply necessary nutrients to plants.