On the west side, ruffed grouse seem to be thickest where alder meets doug fir and there is standing water in pockets of the alder patch.
You'll rarely see them road side during a hard rain (which is often in the fall), but that doesn't mean you can't find them.
Grouse are nervous birds (and rightly so). Hiking through the woods, making a little bit of noise along the way and stopping every 20 yards or so will make a holding bird flush nearly every time as they will think you've stopped because you've found them. You'll hear them before you see them and they won't go far usually 20 - 30 yards tops and will often land in a tree and put themselves on the other side of the trunk. Watch for his head to crank around either side looking at you to see what your up to.
Also be on the ready for more than one bird, particularly early in the season before the current year's broods begin to break up. In Sept it is common to see 3, 4, 5 birds together. By mid Oct you're lucky to come across a pair, and as winter sets in most surviving grouse have been separated from the others and are found solo. There are exceptions however.