Leaf beetles will eat holes in the center of the leaves between the veins. Sometimes this can be confused with slug damage.
Grasshoppers eat from the edge inward and while can eat an entire leaf, usually leaves partial leaves with chunks of edges missing.
A natural control is the house wren... They have a tremendous appetite for the critters [and slugs too]. So put up lots of bird houses and feed the birds in the winter. Don't forget to give these garden helpers several bird baths as well.
If all else fails, you can fall back on insect sprays like Diazinon** for cutworms and Sevin** for the others. Usually one application will bring things under control.
** Please follow label directions and all state and federal regulations on pesticide use