What can I do to improve my chances for a scholarship?
For academic scholarships:
Your ACT and/or SAT scores.
Class Standing
Meaningful Community service
Demonstrated leadership
In that order, is my experience. Class standing is very helpful if you are 1,2, or 3 in your class, then in the top ten percent.
If I had to ascribe weight to the list, I would give 85 to the first, 6 to the second 4 and 4 to the other two, and one percent left for other factors.
Now there are many other scholarships and academic competitions based on other factors. What I have listed are general academic scholarships.
Just a note: Often the last two factors I listed are tie breakers, in case the academics are about even for candidates. I know of one person who won a full scholarship to Med School..while his scores and GPA were excellent as an undergrad, the fact that each Tuesday night he visited a blind couple near campus and did their reading (bills, letters, magazines, newspapers) and writing (bills, mainly) for them as a volunteer. That was the swaying factor for the scholarship, I was told later.
Good luck.