Few decisions will have as lasting an impact on your life as your choice of profession. You can pour your life into a career, only to see it taken away as technology and business attitudes render your specialty obsolete. On the other hand, if you discover that you happen to be great at a job that looks to be in high demand for decades to come, you can practically write your own meal ticket.

But what are the best jobs? CareerCast.com, a targeted career site, recently put together its list of the best and worst jobs in America, which it ranks using a proprietary formula based on the general categories inherent to every job: environment, income, outlook, and stress level. A better environment, a higher income potential, robust future growth, and manageable stress levels all combine to create a great job. The five jobs you're about to see offer the best overall combinations of factors, which makes them the five best jobs in America. Let's see what makes them so appealing.

5: Financial Planner 

Source: Bureau of Labor Statistics Occupational Outlook Handbook.

  • Median pay: $64,750 per year 
  • Entry-level education: Bachelor's degree
  • Number of jobs: 206,800
  • Expected new jobs by 2020: 66,400 (32% growth)

Many of our longtime Foolish readers will certainly appreciate this one, as we do count a number of financial planners among our readership. This profession helps people get their finances in order, whether it's by helping to build a portfolio, minimize a tax burden, or recommend a good insurance policy. Although you can become a financial planner right out of college, many ambitious individuals seek out the Certified Financial Planner certification, which requires a fairly comprehensive course of study. There are only about 68,000 CFPs in the United States, or roughly a third of the total financial planning profession.

4: Audiologist 

Source: Bureau of Labor Statistics Occupational Outlook Handbook.

  • Median pay: $66,660 per year
  • Entry-level education: Doctoral or professional degree
  • Number of jobs: 13,000
  • Expected new jobs by 2020: 4,800 (37% growth)

This is a small but vital part of the health-care community, and it will only grow in importance as more baby boomers find that their years of listening to the Rolling Stones or Steely Dan or [insert your favorite band here, boomers] at full volume has left them with hearing that's a bit less than perfect. Because of their large niche population but small base of employment, most audiologists operate with less competitive pressure than other medical professionals, as is the case with general-practice doctors, dentists, optometrists, and the like. According to Gallaudet University, more than 38 million people in the United States are deaf or hard of hearing  -- that's nearly 3,000 patients per audiologist.

3: Software Engineer 

Source: Bureau of Labor Statistics Occupational Outlook Handbook.

  • Median pay: $90,530 per year 
  • Entry-level education: Bachelor's degree
  • Number of jobs: 913,100
  • Expected new jobs by 2020: 270,900 (30% growth)

How many times have you heard (or said) that computer programming seems like a pretty great job? Many of the best companies to work for are major employers of software engineers. The Fool's own list of the 25 best companies in America has three: Google (NASDAQ:GOOGL), Akamai (NASDAQ:AKAM), and IBM. Google and Akamai also place highly on Glassdoor's latest Best Places to Work list, which is topped by Facebook (NASDAQ:FB), one of the few companies to inspire an award-winning film about (among other things) coding software.

All told, 18 of Glassdoor's top 50 companies are heavily involved in software engineering, and competition is fierce for the best workers. Hours can be long and stress can escalate when deadlines loom, but most software engineers have a genuine appreciation for the complexity and value of their work -- as do their employers. At the highest level, software engineers have perhaps one of the best opportunities to become independently wealthy out of any profession. Just ask any of Google or Facebook's early employees, generously rewarded with stock options.

2: Biomedical Engineer 

Source: Bureau of Labor Statistics Occupational Outlook Handbook.

  • Median pay:$81,540 per year
  • Entry-level education: Bachelor's degree
  • Number of jobs: 15,700
  • Expected new jobs by 2020: 9,700 (62% growth)

CareerCast explains the difference between biomedical engineers and other engineers as "breadth vs. depth." These generalists need to have the ability to interact with a variety of professionals across the medical spectrum, including researchers, physicians, pharmaceutical and device manufacturers, and salesmen for those manufacturers, tying in diverse concerns and inputs to create effective solutions.

Think of biomedical engineers as battlefield commanders in the war for medical progress -- it's not easy to command a battle, but the right mind can make a tremendous difference in the course of the war. That's probably a big reason employment numbers are so low in this field. You can't teach someone to be a good commander. You can enhance latent skills, but not everyone has the ability to think in broad medical strokes.

1: Actuary 

Source: Bureau of Labor Statistics Occupational Outlook Handbook.

  • Median pay: $87,650 per year 
  • Entry-level education: Bachelor's degree
  • Number of jobs: 21,700
  • Expected new jobs by 2020: 5,800 (27% growth)

Don't let the bland picture fool you. Actuaries bring the mathematical and statistical skills to pay the bills, helping clients and companies assess various financial risks and develop policies to minimize those risks. It's not easy to become an actuary, as you need to pass three exams just to earn your bona fides. The position can also be somewhat stressful, particularly if a risk assessment turns out to be very, very wrong. Financial crisis, anyone? Still, an actuary's skills are critical for many businesses, particularly those (and this is most businesses) that rely on complex marketplaces that are nearly impossible for the average person to predict.

The best of the rest
CareerCast has a deep list of jobs, ranked from 1 (the best) all the way to 200 (the worst). You can see the top 20 here, and you can continue browsing to see where your job ranks. Medical and technical jobs dominate the top rankings, but there plenty of surprises to be seen. Are you lucky (or talented) enough to have one of the best jobs in America? Let the world know how you feel about these rankings by leaving a comment below.