Good rule of thumb at Breck: if you're getting on a high-speed quad, you'll likely run into good blue and green terrain. More specifically, hit the groomers on Peak 9 early in the morning, the crowds can be atrocious by 10 or 11. Peak 10 might have some harder blue terrain - best to stay away from the Falcon lift until you're comfortable on the other blue stuff. Wide groomers can be found off Peak 8. Like someone else said, Peak 7 is great and probably the best way to avoid crowds. If you really like Peak 9 but not the crowds, head over to Mercury lift and ski off that.
Copper - if you read much about the place it will say "naturally divided terrain". Very true. Easiest terrain is at the far (west) end of the resort and it gets progressively harder as you work your way back to the entrance. Pass up Kokomo and Lumberjack lifts and start on American Flyer, move to Timberline (look for Soliloquiy as a nice run over in that area followed by Windsong). Rendezvous is a great lift and you can a lot of fun skiing the greens in that area. Plus, no one seems to know it exists. When you head to the other side of the mountain, go up the Poma lift (Storm King) all the way to the top of the mountain. It's a breathtaking view and practically a green run skiing back down to the base of the lift. Before you head down, take a moment to look over the edge of Spaulding Bowl; the view down Patrol Chutes is inspiring. The blue runs off Excelerator, American Eagle, and Superbee are all comparable but you'll find a lot less crowds on Bouncer and Collage (check the grooming report first, they can be unpleasant when bumped out.) For fun, I'd also recommend dropping off the backside from the top of Rendezvous - you can ski the road down to the bottom of Blackjack and come back out of Copper Bowl.