Listen for the birds. They will make a pucking sound, sort of similar to content chickens. They will also almost coo to each other.
If you flush a bird but don't get a shot or miss, try to watch where it heads. They rarely seem to fly more than a hundred feet or so, and if you follow slowly you can hopefully get a second opportunity at a shot.
Crops on my last few birds held wild clover, slugs and red berries.
If you find one grouse, there is a good possibility that more are close by. Even after missing a shot at a bird, I've bent down to pick up my shell only to have a 2nd, 3rd or 4th bird flush from only feet away. Even when approaching a dead or flapping bird, be ready. Unless your injured bird is out of sight. Then devote full attention to getting eyes, and possibly a follow up shot on the bird you've already hit.
And grouse appear like the Cheshire cat. They frequently appear on the trail behind me, just minutes after I've walked by. Last night I walked my two nosy hounds down a trail close to home. No birds heading out, 2 birds coming back on a 30 minute walk. I've had as much luck doubling back on a trail I've just walked as on the first walk out. I flushed 8 birds on Saturday and 6 of them were on the way back to the trail head where I'd walked only minutes before. Almost seems like it stirs em up...
And since the weather has been crap, birds seem to really like the sunny breaks or lighter drizzle on a rainy day and will take the opportunity to get out when the weather breaks a bit.
Also, keep in mind that moose season is opening up for a lot of the province this weekend.