Grades, study skills, lots of reading are equally important. Start getting a handle on the quality of the HS guidance counselor. Make sure your son is taking the hardest classes he can successfully navigate.
Begin to get a handle on the colleges you can afford and which may interest you (the list will evolve up until the end). Use every family trip to drop by a college (any college will do) so your son can begin to get a feel.
A 2020 has the chance to really push his academics; the higher the better - so many more options.