Who will graduate from college?
According to a study discussed by Unbossed, socioeconomic status (including ethnicity) and high school curriculum are the best predictors of success. A rigorous academic course load including multiple AP classes and at least pre-Algebra, and an absence of remedial classes in high school is key. The other key point is to go to college immediately after high school and to maintain a full course load while there, without withdrawing from courses.
Unbossed also notes that the key factor in success in high school is one's reading and math abilities going into high school. You can't avoid remedial math and reading classes in high school, if you don't make it to high school level in these key areas by the time you complete the eighth grade.