Kudos for thinking about this so early in your HS career. In general, you will want to take the most challenging course load that your school offers but at the same time focus on the subjects that interest you the most. You didn’t mention which college you want to apply to, but given the math and science focus of your question I’m going to assume MCS, CoE, or SCS.
I’m also going to assume that you can realistically handle the course load. Don’t kill yourself and spend your HS years in misery trying to improve your chances on getting into a single “dream school”. There are so many excellent colleges available that it simply is not worth taking on too much if you would be happier and less stressed taking some honors courses or “fun” electives instead of APs.
For math, the most challenging course load will most likely mean Calc AB in 11th grade and Calc BC (essentially Calc 2) in 12th grade. AP Statistics is fine for an elective, but Calc BC is more challenging. You may have IB or Dual Enrollment options as well, but since you focused on APs in your original post I will just discuss APs.
For science, I’m guessing you’ll be doing Honors Chem in 10th grade. You’ll then have options for AP Bio, AP Chem, and two AP Physics C classes for 11th and 12th grades. At a minimum, plan on AP Physics C - Mechanics. The other AP science course is up to you.
For Social Sciences, AP Human Geography, AP World History, AP US History would be a pretty typical lineup for 9th-11th grades. For 12th grade, you’re probably looking at one of the AP Economics/US Government courses (whatever your school offers).
You didn’t mention foreign languages, but you’re going to want to have four years in the same language. If possible, take the AP class in 12th grade. I don’t think CMU requires foreign language courses within their Core Curriculum (at least they didn’t when I was there), but they will want to see this in your HS transcript.
For electives, I would suggest that you follow your passions. This will help tell the story of you when you apply. AP Environmental Science, AP Computer Science, and AP Statistics are great options. However, don’t rule out other options. For example, if you are interested in art, take art electives and look for ways to tie your interest in art back to the colleges you plan on applying to.
Check CMU’s website for the credits they offer for each AP exam and what requirements they have in their Core Curriculum (http://www.cmu.edu/hub/registration/docs/ap-credit.pdf). It’s very likely that you won’t be able to get credit for every AP course that you take (even if you get 5’s on all tests) due to the requirements of your major. Unfortunately, it doesn’t look like scoring 5’s in AP Lit and Comp will help you avoid CMU’s writing requirement. You will still need to take 76-101.