If its at all possible, try to find someone to ski with that really knows the mountain. I have a pass to Breck, and the only time that I ski Breck is with people who know the mountain. At all costs, do not go to any of the bases (except for maybe peak 10). They will be crowded, no matter what, I've been there on a Thursday because I had a off day from school and the lines were at least 15 minutes, I know that may not seem like much compared to weekends, but when I went to Keystone the following day, the longest I had to wait in any of the lift lines was less than a minute of standing time. However, there is hope, get there at first chair, and I mean literally first chair. I was able to take 12 laps of perfect groomers and rollers on Peak 7 with the longest lines being less than 5 minutes before the crowds came, then I went to the T-Bar and did 3 laps before more crowds came (T-Bar can get pretty crowded). The point is there is usually a way to miss crowds, and if you cant miss the crowds, you still had a pretty good day. Another good time waster to have a good day still even if there are crowds is to do some hike terrain. One day I hiked Whale's Tail 3 times, Lake Chutes 4 times, and the hike to terrain off the top of peak 9 twice. and that was still with my at least 8 laps on peak 7. That was all mostly extreme terrain, but if you are more of a park skier you could hike features in the park. Also, do not eat lunch at the base, Vista Haus is a pretty good place to eat.
Sparknotes: Breck is unavoidably crowded, ski with someone who know the mountain, get there early, hike, do go to the bases.
Have fun and good luck
Funny guy: If I were ever a surgeon I would have to resist the ultimate temptation of squeezing peoples intestines like a tube of toothpaste"
Me: I'm never brushing my teeth again