Job requirements vary from state to state, but you'll generally need to go through a number of massage therapy courses as well as pass an exam before becoming certified or licensed to practice (source). To pass the exam, you must either answer a certain number of questions correctly, or else massage a good grade out of the test administrator (we work those puns).
If there's one thing certification boards like to see, it's you at the table putting your acquired skills to good use. In addition to an exam, you'll be required to do a massive amount of field work—anywhere from 300 to 1000 hours working on clients who are paying discount rates for your inexperienced handiwork.
While not technically a requirement, it does help to be personable and friendly. These folks (your clients, not the teachers) are generally naked and vulnerable, and won't be cool being poked and prodded by someone with resting mean face. You're here to sooth and relax people, not make them feel like they're being punished for something.