How to choose a career?
It depends on what your goals are.
If you are a practicing Buddhist who’s goal is to become enlightened, my advice is to find a profession that will bring about as little discomfort and personal conflict as possible. Work that brings anger, guilt, frustration, etc will naturally be distracting from your goal, and will make it more difficult to achieve. You want to find a job that you won’t “take home” with you. One that doesn’t encourage suffering within yourself. Or, if you have the luxury, become a monk! Becoming a monk is the fast track to removing yourself from situations that impede progress towards enlightenment. The bottom line here is, if you want to become enlightened, do a job that isn’t going to distract you from your goal.
If you are a practicing Buddhist who’s goal is just to live under the guidance of teachings, I would suggest just choosing a job that doesn’t violate the precepts. That way you can feel good about what you are doing, and will run into less conflict overall.