Go to film school or start in the business as a PA. Even if you go to film school, get a job as a production assistant after you graduate. The on-set experience is priceless. You'll get to learn more than you could ever learn from school in the practical sense of how things actually work and what to do when unexpected events occur.
Get into the development offices. Start from the bottom as a script reader. You'll read thousands of scripts and recommend those you think have great ideas, stellar writing or are superb overall to your overseeing producer. The more you read and the more you conference with the producer about the scripts the more and more you'll start to see what makes a script great and then how that becomes a good movie.
Ask to work towards the goal of being a film executive. It may sound silly but if you make your intentions and goals known then back them up by working hard you'll find that there are people who will actually help you get there and push you in the right direction.
Work your way up the development chain. Once you're at a solid development executive job you can start showing the higher ups that you know what you're doing by selecting quality material and getting things done. Seek out the next blockbuster or independent surprise and you'll be rewarded. Then show the studio heads that you can do more by overseeing some projects from other people (those that are not your own projects) or making predictions on them. Start predicting their box office numbers. The more you can get right the more the heads will look at you and realize you know what you're doing.
Create a plan. Draw up a plan for a new innovative film technique, marketing campaign, studio construction or legal issue and you'll stand out in a second. Studios want executives who are on the cutting edge and can spot and create new trends and products even before the technicians and markets get wind of it. They want forward thinkers and innovators. Become an innovator and you'll be promoted to film executive.