SAT: 1590 SAT (old SAT out of 1600)
SAT IIs: 800 Math II, 800 Physics, 800 Chemistry, 790 US History
APs: 5 APs at time of admission (all 5's), and 6 more senior year (all 5's)
ACT: 35
ECs:
-Captain of Quizbowl team
-Editor in Chief of Newspaper
-Founder/Captain of Computer Science Team (and within the CS Team, started a community service program with old age home), among top students at American CS League and USA Computing Olympiad competitions
-Vice President of Debate Team (top ranked debater in school, ranked nationally)
-Director General (equivalent to VP) of Model UN
-No club position on Math Team (too committed elsewhere), but performed well in AMC 12, AIME, and qualified for USAMO (USA Mathematical Olympiad)
-Semifinalist in USAPhO (USA Physics Olympiad), USNChO (US National Chemistry Olympiad), and USABO (USA Biology Olympiad)
That's pretty much most of it. I should emphasize that there's really no "standard mold" you need to fit, though. I was well rounded, and it served me well, but there are also students who are "well-lopsided" (insanely good at one thing) and thus get in. There are plenty of those at Princeton, too (in fact, that's what scared me from pursuing math...the sheer brainpower is very intimidating sometimes).