Unless your last name is Rockefeller, Hilton, or Walton (as in Sam Walton, founder of Wal-Mart — four of the seven richest Americans are Sam's heirs) chances are you had to work for the money you have. If you're not yet retired, you still have years of that work ahead of you. And you retirees aren't completely off the hook, either: Houses and cars need to be repaired, meals need to be cooked, and taxes need to be filed. If you don't do these things yourself, you'll have to pay someone else to do them.

Your ability to turn your labor into a paycheck — or to do things yourself, so you don't have to fund someone else's paycheck — is your “human capital.” This combination of knowledge, experience, talents, work habits, and social skills is perhaps your most important income-producing asset (as I wrote in January).

I've been thinking a lot about “enhancing human capital” over the past couple of years, especially as we've entered the toughest employment environment since the early 1980s. Few people can take their jobs for granted. Too much can change: the economy, technology, competition, even health (affecting one's ability to do a job — approximately one-quarter of retirees stopped working due to health problems).

Then there's the question of how to grow your net worth these days. Cash and bonds are at decades-low yields, and we all know now that the stock market doesn't always go up. Thus, the asset we have the most control over is the one we take a shower with (assuming you do it alone, at least some of the time). A great career can result in a great retirement, because a higher income allows for more savings and retirement benefits.

But let's face it: Earning a higher paycheck isn't easy these days, so it takes deliberate planning, extra work, and perhaps bringing a higher-up into the shower. Since I'm not a human resources expert, I asked one of my Foolish colleagues — Angelique Keenley, Vice President of HR at The Motley Fool — for suggestions. She passed along these 11 ways to improve your income-producing capacity.

1. Keep acquiring degrees and certifications

We can increase our human capital throughout our lives by getting more education and professional certifications and by doing other things that enhance our résumés. Which skills, professional designations, or degrees could you acquire that would make you more valuable? (Don't spend your time or money on just any old degree — get one that counts in your current or desired industry.)

2. Join professional organizations and build a strong network

Higher-level positions are almost always filled by “someone who knew someone,” not by a stranger applying for a job opening.

3. Continue to seek out excellence in your field

We at The Motley Fool call it “deliberate study,” and you don't attain it by just showing up and doing your job every day. Spend time reading blogs, attending conferences, and talking to others in your field who are smarter than you.

4. Network inside your company

Don't pass up opportunities to have lunch with the CEO or other senior leadership. As well as making important friends, you'll learn things about the business that will make you more valuable — and help further your career.

5. Get (or become) a mentor

Seek out someone you admire, either inside or outside your company, who would be interested in helping you grow. And look for ways to mentor those less experienced than you; besides the whole “good karma” thing, it's another way to demonstrate the value you add to your company.

6. Stick around awhile

It's a good idea to stay with your company for at least two years before moving on. A résumé that shows a lot of jumping around can be a definite red flag.

7. Work for little to nothing

If you're looking to make a career change, offer to serve as an intern for someone who's established in the profession you're interested in. You'll see what the job is really like, acquire a few skills, and begin making contacts. And you can always do altruistic volunteer work, even if you're unemployed. You may just meet your next employer there.

8. Take on additional responsibilities

Employers hate it when someone says, “I'll only take on this additional responsibility if you raise my pay.” They love it when you say, “I took this on three months ago, and this is the success I've brought to the company. Can we talk about a raise?” We know someone who took this approach; instead of the $1,200 raise a previous boss had promised, the person's new boss approved a $15,000 increase.

9. Make a difference

Is there anything about your company you can point to and say, “This is all thanks to me” (besides the stains on the carpet)? What about the way you work would be hard to duplicate?

10. Research the trends in your profession and industry

Keep an eye on relevant trade journals (you know, such thrilling real-life publications as Welding Journal, Pig International, Modern Brewery Age, Seed World, Professional Candy Buyer, and Portable Restroom Operator). You'll get the inside scoop on where your industry is headed.

11. Become a do-it-yourselfer

Are you spending a lot of money on something you could learn to do yourself? Besides the monetary benefit, studies show that lifelong learners are less likely to suffer cognitive decline.

J.D.'s note: I'm a huge proponent of personal development. Your career is your most valuable asset, and by becoming a better worker (whether for yourself or for others), you boost your ability to earn. And that doesn't just pay off now — it pays off for decades to come. Here are some other articles on this subject from the GRS archives: “How I Gave Myself a Raise“, “Five Steps to Six Figures in Seven Years“.