Chair #1- If open for skiing, you have a few options: you can go left and drop down behind the rental shop, turn around, and drop down right, where you came up; or traverse up and to the right to hit a double diamond called Bentley's run. Either way you choose to go, you will end up down at the bottom of chair 1. Overall, the length is excellent for this run, covering about 1,300 vertical feet.
Chair #2- When you get off chair #1, go straight and follow the bend around the mountain; this is a short run, but is the only beginner run on the mountain. It's of decent length, and when you get to the bottom, make a left to get on Chair #2 or continue straight towards chair #3. When open, only chair #2 accesses the terrain park with a quarter pipe and various features. Take Chair #2 back up to enjoy the now wider and longer beginner's area and runs.
Chair #3 - The main lift, servicing about 20 runs on this mountain. When you get off, either go left for the easy part or right for the steepest drops in Southern California. To the right, you will find about four (five, if creative) runs and about 15 with numerous drop-offs and tree runs to the left. My favorite run on Chair #3 is, I believe, called Shortcut (no sign really posted), but when you get to the bend on fireroad, which forces you to make a sharp right turn, stop and go straight; it is by far the best and always untouched tree run (besides the backside and sides of Chair #4) in all of Mt. Baldy. There is one very long beginner run on Chair #3 called Mullins Mile (leads to some awesome backcountry, if open).
Chair #4 - When open, this is the favorite of the masses. It has about four long intermediate runs that are the tops of the mountain. So when it is open, Chair #4 is worth the entire lift ticket. Don't get caught, but when Chair #4 is open, make a left and go over the wall of snow, where you see a a cut-in-half, wooden-looking telephone pole. It's advanced tree/open/steep/powder--the best skiing you can find.