Qualifications
In order to be a trial lawyer, you should have an undergraduate degree (source). And contrary to popular opinion, it doesn't matter what you major in. So go ahead, be a drama major while you can. Just don't tell your parents we gave you that advice.
You also need to have a law degree which takes three years to complete. And once you've spent a day celebrating making it through the three most difficult years of your life that was law school, you get to start studying for the Bar Exam for the state in which you choose to practice law.
Of course, you must pass the almighty Bar Exam and also the Multistate Professional Responsibility exam, and then…voilà, you're a lawyer. Time to find some clients and bring home the bacon.