According to the Bureau of Labor Statistics of the U.S. Department of Labor, people change jobs, on average, ten times during a twenty-year period. More shocking is that baby boomers continue to have a relatively large number of short-duration jobs even as they approach middle age.
( Department of Labor USDL 04 -1678 - Wednesday, August 25, 2004)

I work with a lot of clients, and know a lot of friends and co-workers, who either want to or need to change careers.  Here are a few examples of successful transitions:

• Literary agent to marketing consultant
• Engineer to landscape architect
• TV editor to instructional designer
• HR professional to college professor
• Sales professional to nurse
• Engineer to entrepreneur
• Entertainment executive to not-for-profit leader
• Paralegal to lawyer
• Teacher to chef

What do you need to do to have a successful career change? Find a new area of work which you are attracted to; which fits your needs (or some of them) for a job e.g. working in a team, being in a large company etc.; and where there is a demand.

Research what that job requires.  Talk to friends and find someone who works in that industry or job.  Contact companies and ask to do an informational interview.  Read what you can on this work.
Find out how other people start in this career.  Do you need to go back to school?  Can you get government assistance or a loan or a scholarship or will family or friends invest in your education?  Do you have to start at the bottom?  What is the minimum you need to get paid to survive? What contacts do you have in this new world?  Who can you network with?

What skills do you have?  What transfers to the new job?  How can you prove that you can do the job?  Can you work on probation, volunteer, intern or put together a proposal that shows you can do the job.  What knowledge gaps do you have?  How can you show you can fill them?  What is your experience of learning new things?  How does that translate to the career change?

What's your plan?  Who do you need to contact?  What do you need to present - resume, bio, marketing materials if you want to run your own business?  Who is your team - best friend, coach, job search buddy (keep each other motivated and accountable), accountant, SCORE business counselor, career counselor, professor etc.

The Big Ones!  How will you survive as you change careers?  Do you need a part-time job?  Can you use savings?  Can you borrow (and still be OK economically).  Can you sell something?  Do you need to relocate?  With family or friends to save rent?  To a cheaper location? To a state where they pay for training or have a good deal on college fees or rent.  Or to another country where your talents are in demand, you make more money or your resources go further.