In this thread I will use all of my knowledge to briefly tell you how you know if you will get in or not.
There are a few different factors, which I will call Numbers (GPA and SAT/ACT), ECs, Personality (reported by recs and essays), and Political.
We all know what they want in Numbers: for them to be as high as possible. The same is roughly true when it comes to ECs - they want quality ECs (emphasis on the S) that impress and show leadership and initiative. The reason for this is because these schools are trying to draw in the best genetic stock (in their eyes), and good leadership signals people like you, meaning you will be good for the reputation of the school, and you may go on to make a big impact on the world, which the school can take credit for.
Personality is the point where people get confused as to what these schools want. But in my experience, and I have great certainty when I relay this info, colleges want the following: passion, conscientiousness, obedience, and extroversion. By extroversion I don't mean "likes to party", instead I mean an orientation towards the "Other" as opposed to the self. Extroversion in this sense is signaled by a pervasive concern with what others are up to, while introversion would mean a lack of concern with the affairs of other homo sapiens. As for the other qualities colleges want, these things ultimately predict future success. The opposite of conscientiousness is laziness; colleges don't want lazy students. The opposite of passion is apathy, and indeed, it is passion which drives conscientiousness in many cases -- those two are linked. Obedience may draw some contention from readers, but its opposite is rebelliousness, and colleges don't want students who will protest all the time on campus, create disorder, and defy the Faculty. They would be masochists if they liked to be told "no" by students. Why wouldn't they avoid that conflict by screening for obedience? Furthermore, obedience is actually a success predictor to an extent, especially when it is present with properly channeled passion. Most win by climbing hierarchies, not creating new ones. I tell you, if you signal these four qualities well in writing, they will love you as an applicant.
Last but not least is the Political. Let's keep it real here: if you are double plus unwhite, unrich, and unadvantaged, then you are triple plus diverse and colleges are currently obsessed with "Diiiiiversssityyyy." This diversity is primarily racial, secondarily economic, and thirdly geographic. Hitting the checkboxes will benefit you in that order. For elite colleges, legacy also helps. But those are the things you can't control -- here's what you can: they also want friends of Diversity. If you signal you love diversity it will not hurt. It should actually help. But do not under any circumstances criticize their very criticizable politics at all. In fact, if you are rich and white, then it is a good idea to signal that you love diversity to prevent them from assuming you are against it.
Hope this helps!