Successful restaurateurs agree that the best preparation for owning a restaurant is to work in someone else's first. Think of it as getting paid to be educated. Certainly you should read books and take courses, but you should also plan to work in a restaurant for at least a few years doing as many different jobs as possible. And if you're not actually doing the job, pay attention to the person who is--you may find yourself doing it when your own restaurant is unexpectedly shorthanded.
Ideally, you should work in a restaurant similar to the type you want to open. You may find you don't like the business. Or you may find you're more suited to a different type of operation than you originally thought. Hopefully, you'll discover you're in exactly the right place.