First of all, determining what the top postdoc career positions are is really secondary to determining what you would like to do. If you've already gone to school and have gotten your undergraduate degree, you probably already know what you want to do with your career and whether or not you're going to need a postdoc degree.
So take a look at your field. What is it that you're going to do your doctorate in? If you're not yet in a position to pursue your doctorate, take a look at fields that prefer applicants with doctoral degrees and see if you have talent in one of them. Of course, your first priority is going to be that you like your job and have the skill to do it.
What are some postdoc careers that prefer or require people with doctoral degrees?
The academic world
The academic world is of course a field that is rife with those who have doctorate degrees. Most professors (if not all of them, eventually) hold doctorate degrees in the fields they teach in. The academic world can be a tough one, because both tenure and competition mean that these jobs can be quite rare. If you are determined to have a career in academia, it's most likely that you'll begin as an associate or junior professor and then work your way up. These days especially, getting tenure is also questionable, quite often, for those who teach in the postsecondary educational field. Eventually, if you stay in the field and are good at what you do, it's likely that you'll get it.
The pharmaceutical or biotechnology industries
Biotechnology and pharmaceutical industry are among the fastest-growing fields, currently, and they also require a lot of candidates who have postdoctoral degrees. One of these is a medical scientist. A medical scientist studies the human body and its diseases so as to improve overall health and condition in general. They may conduct research and development in the biomedical field specifically to learn more about the human body and the things that affect it, like agents of infection, including bacteria and viruses. Medical scientists have been very important to the field of medicine, because their work has meant that there have been advances in the treatment and prevention of many diseases, including those that have previously been poorly treated, entirely untreatable, or even deadly. This is one of the more difficult fields to get into, specifically because economic conditions at present may minimize the amount of money that's available for research and development in these fields.
Engineering
Many different types of engineering jobs require that candidates eventually get their postdoctoral degrees as they continue through their careers. One good thing about this particular field is that it encompasses a number of different areas, so that you can choose your passion and then go with it. Another good thing about choosing engineering as a profession is that you can begin with a bachelor's degree in engineering or a related field and continue your education even as you continue to work; some employers even pay for employees' educations for their doctoral degrees as long as they're qualified for advancement once they get that degree.
Some pointers about getting top postdoctoral positions
In most cases, you're not going to simply go to school until you get your doctorate and then begin to work. Instead, what happens is that you start your career with a bachelor's or maybe a master's degree, and then continue your career but pursue education at the same time until you've got your doctorate degree. In many cases, your field may even require you to eventually obtain a postdoctoral degree as you advance through your career, and for this reason many employers actually help offset educational costs, if not provide educational costs outright, for their employees who are qualified to pursue doctoral degrees.
Getting the job
Again, it's likely that you are going to start your career in your profession with just a bachelor's or maybe a master's degree. Your school may be able to help you with placement in a job that is naturally going to provide continuing education as a matter of course. And of course, you can also search the Internet for these types of positions, since many jobsites also post positions that require these types of qualifications.
In fact, it should make you hopeful to note that if you get an entry-level job with a bachelor's or master's degree and continue to pursue your education as you work, you'll have a leg up over candidates who have stayed in school to pursue their doctorates to the exclusion of having work experience as well. That's simply because real world experience is far superior to education pursued in a vacuum, especially when that experience is combined with a proper educational background.
