I was accepted to Michigan but chose to go to the University of Texas because out-of-state tuition is so incredibly high. On my academic tour of the campus the counselor broke down how they look at potential students
Grades and rigor of academic classes: I was enrolled in lots of AP courses and made good grades (top 10% of my class).
Extracurriculars: Lots of volunteering, community service (National Honor Society looks great), and perhaps a job or internship.
Application essays: Make it personal, make it believable, make it something you are knowledgeable about - don't sound like you copied and pasted from somewhere.
Teacher rec letters: Teachers have to be able to write favorably about your child from a classroom and personal perspective. Advise your child to really get to know a few of his high school teachers well, as well as the guidance counselor
Hope this helps!