Pruning an Ornamental Grass
Trimming back an ornamental grass is fairly straight forward. For miscanthus I trim down to 6 inches or so high and take small handfuls of grass at a time then prune them with my hand clippers. For other grasses I make sure to stay 4-6 inches above the crown of the plant. I kind of use the top of the green growth as a guideline. As far as tools go I use the low-tech hand clipper option, but I don't recommend it! It wears out your arm very fast and the clipper blades even faster. A good pair of electric trimmers will make "short" work of your grasses but a pair of sharp pruners will do a good job too. I also recommend using good thick gloves or you risk a painful death by a thousand paper cuts. It's not really paper, and you won't really die, but paper cuts are one of the most annoying injuries you can receive and these grasses have very sharp edges.
Have you pruned back your grasses yet?