Job requirements vary from state to state, but you will generally need to go through a number of massage therapy courses as well as pass an exam before becoming certified or licensed to practice. 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. They do like to see you putting your acquired skills to good use. In addition to an exam, you'll be required to work a massive amount of field work, something in the 300 hours range giving massages to would-be clients at highly discounted rates.
While it is not technically a requirement, it does help to be personable and friendly. People don't usually like their naked flesh to be poked and prodded by someone with an angry look on their face. The world went through enough of that during the Inquisition and their last IRS audit.