They're one of the first fish to move into the upper ends of rivers around here in the early spring to spawn. It's already happened, doesn't last long, then they scatter into the river systems. When I was a kid, I would start fishing for them in late Feb & early March, usually with minnows below a float & when I started catching them, then start throwing flies or lures.
I've done well with small, simple streamers & wet flies. Otherwise, I've caught them while targeting other species. Most any fly that imitates baitfish will work, and they'll eat various insects too, both aquatic & terrestrial.
I've caught them too while fishing with various lures for bass, such as crankbaits & spinnerbaits. Small spoons & spinners work well.
I posted some flies awhile back that I had tied & to which I had added small single blade spinners. I've caught a lot of Yellow Perch on that fly & spinner combination.
As theboz has said, they're not picky!
Here's the flies I had posted previously. All are size 4.