You are working on the Master's or PhD, and you are certain you are not continuing on with academia. You already have a job (postdoc or otherwise) and you want to switch careers. How do you do that? Here are some examples.
Roger wants to go into patent law, but is working on his molecular genetics PhD. Law firms only intern law students. He finds law firms that deal with patent issues, contacts a lawyer with a PhD. He tells them about his situation and asks them if he can volunteer or job shadow them to see what it's like. Roger interns for free once a week, and makes up for labtime on the weekend. He may or may not like it, but now he knows. If he likes it, he can stay and chances are, he will be hired as a scientific consultant while he studies for the patent officer exam. The lawyers have all been students too. Most, if not all, of them will want to help you out. A friend of mine finished his postdoc, worked as a Technical Consultant for a law firm for a year or two, then the firm paid for his law school. He is now a patent attorney.
Shelley is working on her Master's in protein biochemistry and knows she wants to be in bioinformatics. She find courses and takes relevant courses in the computer science department while still maintaining full lab work working later at night and on weekends. She graduates with an MSc in Biochemistry, but has the computer programming to look for a job in bioinformatics. She attends a job conference, talks to some company booths, receives an interview and lands the job. Many years later, she is the Director.
Jane wants to be a science writer/editor. During her graduate years, she writes articles for the campus paper, mainly about science issues, and becomes experienced in publishing the news for the general public. She calls other science editors and interns for free one afternoon a week. She makes up for labtime at night. After her defense, the science magazine hires her.
Lauren has been a Principal Consultant for Management Consulting for many years, but wants to serve non-profit organization. She donates her skills once a week and sits on advisory board for a non-profit sector. The next year, she is hired by the organization and is now the Director.
The common theme here is that the transition year or years will mean you may have to intern for free, volunteer as you learn what the new occupation is all about. What is driving you to be there? Not fear, a PI, the educational requirements of a university, parent's expectations, a boss, or money. It is your own passion and desire to be who you want to be. That, is a powerful force. And only you can drive it there.