A good chef is someone who has studied long and hard to learn how to be a part of a successful kitchen and prepare great food for their customers. A great chef is that and something more -- but what that something more is can be elusive so we'll just focus on the practicalities.
It takes many years to become a chef. Most begin by working in some sort of apprenticeship, be it formal or informal (a paid commis position or as a part-timer). Early experience in a kitchen will give you a good understanding of just what it takes to become a chef.
In this capacity, you'll begin by cleaning up and little more. As you show some interest and aptitude for the job, you'll get a chance to help out with cutting vegetables and stocking shelves. It might sound boring but it's vital experience that will stand you in good stead later in your career; great chefs understand every aspect of the kitchen.
Chefs have formal qualifications as well as practical experience. College courses offer extensive training, not just in food preparation and service but in all aspects of your chosen career. Business, health and safety and people skills are all dealt with. Maths, communications, even foreign languages may be on the curriculum. Consider your options carefully when choosing a course. Look for a well respected course from a good college. Take note of the facilities they offer and how much practical experience you will get as part of the course. Try to go for a good mix of all of the elements of food catering.
You'll need to study hard and work even harder but advancement as a chef is, in some ways, easier than in other careers; there's an obvious and well recognised career path. You always have the opportunity to prove yourself and to advance because of that. In fact, this is one of the few careers where moving job often is a good thing. The most common positions in a kitchen range from Commis, Pastry Chef, Saucier, Sous Chef, up to Executive Chef. The latter must understand all of the other positions to be able to run a successful kitchen. There are other specialties too: Garde Manger, Personal Chefs, Gourmet Chefs. At some point you will need to define the area you want to focus on but, before you can do that, you need to have the basics covered and still have your passion for food and your enthusiasm for the job.