How do I know which career would be best for me?

Links:
http://www.helpguide.org/life/finding_career.htm
http://www.bppe.ca.gov/forms_pubs/career.shtml
http://money.usnews.com/money/blogs/outside-voices-careers/2010/12/06/how-to-choose-a-career-thats-best-for-you

Summary:
   To find the career that best fits you, there are several factors you should count. Among those factors, you find: yours skills, interests, expectations. First, think about what do like to do or what comes easy for you. When you identify that, you can get involved in activities or classes to help you develop that skills and/or put it in practice. You can also do career test to get an idea of what you're really good at. You might not like what your results suggest but maybe it will make you think about what you're really good at and help you look/research about careers that require those skills that you have.
    If you discover that you are interested in a certain area, then you can start looking for jobs that have to do with it. You can also ask people that have certain jobs that catch your attention, and find out more about those jobs. Also think about what jobs are going to be in demand and promise you a great future.

Question:
What careers are or will be in demand?