This is a question that has come up a few times in the Financial Aid Office that I thought you might be interested in.
Remember that scholarships are awarded based off of some form of merit, ethnicity, talent, or need. Basically, you have to do or be something to be awarded a scholarship. Some examples would be your writing an essay, your living in a specific location, your being a member of a specific ethnic background, or your grades. Obviously you have control over your grades, but you can't change most of the other elements. So, how do you get ahead of the competition?
The simplest way of helping yourself out is by trying to obtain scholarships with the smallest opposition. What does that mean?
Think of it this way. If you are a female, and you enter a scholarship contest that is open to women, then you will have a lot of competition: women of all ages across the country and maybe the world. But if you enter a contest that is open for women, age 18-22, in the Santa Fe region, for Native Americans, then you will have much less competition just because there will be fewer that will be eligible. Any of those specifics will eliminate a number of applicants, which will raise your odds.
You definitely will want to enter both competitions in the examples above, but your odds of winning the first is much less than that second, so don't be surprised if you don't win the first. Also, typically, unless there's a special competition, the second scholarship example will dole out more money since fewer applicants can be awarded for it.
However, when in doubt, apply for every scholarship you can. The worst that will happen is that you won't get it. They cost nothing, and they cost nothing to enter, so you're losing nothing by trying. Also, the hard work and the researching will be good practice for college. So good luck in your searches!