Think long and hard before you decide on becoming an ATC. It's a difficult and extremely stressful job, and very few people make it through the selection process. But if you do make it, it's also very rewarding and challenging. Much better than your typical desk job!
Training for this career is difficult as the standards for receiving certification are subjective, at best. Success depends on meeting the individual instructor's requirements - sometimes related to job performance, and sometimes related to external factors such as taking them out to the bar on a regular basis. The job itself is rather fun, however the training is a brutal waste of time, given that only 3-5% of students actually succeed in their training.