All recent college graduates should begin to think about investing if they haven't already started to save.

Yes, there are student loans and a job search to think about. But once landing that first position, the human resources department will ask a critically important question: "Do you want to sign up for our 401(K) plan?"

To become better informed, read'sJim Cramer's book, Get Rich Carefully, and then simply check yes to contributing to a 401(k), preferably choosing to max out at 15% of annual income.

Of course, it is always best to check with an accountant to determine whether a 401(k) or individual retirement account is the best choice. A Roth IRA can be a great choice for younger people, and it is also important to consider the fees associated with a company's 401(k) and the investment options available.

The time value of money is so simple, one would think it wouldn't even need to be mentioned. Unfortunately, many investors aren't aware of this important concept, and so they don't max out their 401(k)s, 403(b)s or self-employed retirement accounts.

My mother's retirement savings method was extraordinary, so I would like to share it with recent graduates and hopefully pass on her wisdom. Her finance education was nothing more than a bookkeeping class she took in high school, but she was a walking MBA.

Meanwhile, my father flunked seventh grade three times due to something related to the school basketball team. He started and failed in six businesses, narrowly escaping a second bankruptcy.

My family had a dry cleaning business, and the first thing my mother did when they started the business was to hire an accountant. The accountant told my mother to keep my father away from the books.

On my ninth birthday, I was informed that I needed to start helping with the Friday payroll, and my mom told me about her background fund that I wasn't allowed to discuss with my father.

The way this worked was if the business took in $200 in a day but had $100 in bills to pay, mom would only record the balance as $100 so my dad would think they were broke. My mom and I kept up this charade for 27 years.

At age 65, my parents stopped by a Cadillac dealer.

Mom pointed to a powder blue new Cadillac and asked dad, "Do you like this one?"

When he nodded, mom looked at the salesman and said, "We'll take this one."

She wrote a check, turned to my dad and told him he could retire.

One of my brokerage clients was a cartoonist. She took this story and made it into a cartoon booklet, and I handed out 2,000 copies to help build my business. 

What does this have to do with the cardinal rule of investing? The most important lesson my mother taught me was, pay yourself first.

For those who heed my mother's advice, here is what can happen, based on historical stock market performance.

Let's say someone is 25 and gets their first job that pays $40,000 a year. Setting aside 15% of pretax earnings would mean contributing $6,000 a year into a 401(k), instead of losing a chunk of that money to the Internal Revenue Service.

Assuming that this same person works 35 years until they are 60 and using an 8% average estimated growth rate or total return with dividends and capital gains reinvested, the estimate future value of the 401(k) is $1.12 million.

And liquidating or receiving dividends and capital gains equal to 5% of portfolio income each year during retirement amounts to $55,830 in estimated annual investment income.

Most people can comfortably retire on 70% of their current income, and most should be earning more at 60 than at 25.

Sadly, however, it isn't unusual for a 45-year-old to have saved nothing for retirement.

If a person earning $40,000 started saving for retirement at 45, and put $6,000 into a 401(k) each year, with 15 years until retirement an an average estimated growth rate of 8%, that would only get them $175,945. And 5% of that would generate an estimated $8,797 a year in income.

The examples illustrate the power of the time value of money.

We read so many sad stories about athletes and celebrities who made millions and then lost it all, but sometimes those with jobs like teachers are the best savers, perhaps because of their steady paychecks and expertise in education.

Make sure to pencil in 10 minutes each year to update the retirement fund contribution amount on an annual basis. There are an abundance of retirement estimators available online.

Very few people end up sorry that they saved all that money.

This article is commentary by an independent contributor.