Congrats on being a national merit scholar btw. I hope you got a major sign on bonus wherever you agreed to go to college. You should have found a program at your future university that provided a summer research job with room and board, that's what I did so I left for college two days after HS graduation with a job. I was a national merit scholar too, and it doesn't mean much after you graduate college. Might be the only HS honor that might still be worth putting on a resume. I had 47 hours of college credit leaving high school, do yourself a big favor and research college grad requirements thoroughly right away, and always ask if a particular class fulfills a particular requirement, since this is often counterintuitive.
1. Register with a local temp agency. If you are only going to be available to work for the summer, this is your best shot. For that matter, register with all of the local temp agencies.
2. As has been said, taylor your resume for each application, most people don't care about your gpa or test scores, they just want someone who can follow orders, come to work ontime and sober, and smile at the customers constantly like an idiot. $5 and a 4.0 gpa can get you a cup of coffee.
3. The current job market is uber sh!tty, so don't feel bad when you don't get hired. My wife graduated a year ago with two BS degrees, one in chemistry the other in biology. Though she got a summer job right away, and has filled out 3 applications per day since last september, and gotten dozens of interviews, she still does not have a position using her degrees. (She did just start a temp position that requires a degree, but not her degrees in particular.) I just got hired myself, and it may be of interest that my prospective employer knows, and talked to, my previous employer (from a position with similar responsibilities). Lesson: You need connections within your prospective industry.
4. Most of the time your application goes to a human resources department. HR workers do not know from your resume if you qualify for a position, you have to call and explain to them why you qualify. They do not know that having two college science degrees means that you have more than 40 hours of science college credit. By the time your application even gets through human resources to the hiring manager, the hiring manager has already decided to hire someone else who was recommended by a friend of his.
5. To make connections in the industry, find an excuse to talk to insiders about subjects of common interest. ie., if you want to do research on gene therapy in mice, then read all the papers by a local researcher, then email an intelligent question about it. Start up an intelligent discourse, eventually the person will become familiar with you. Familiarity can provide a big advantage. If you can find a way to help them somehow, it will demonstrate your utility. Don't sell yourself, sell what you can do to help the company profit.
6. The money and wages you will make prior to college graduation are worth little compared to the job experience. If you can maintain some sort of part time position that's only a few hours a week throughout your college career, and then get full time jobs during the summer, it will make post-graduation job searching much easier.