Thakor likes the image of online banking as an air-traffic-control tower, with bills and expenses as planes zooming at you. "If you don't have a command central to monitor that, you could get yourself in trouble," she says.

Bank tools such as low-balance alerts (although you should be aware of every transaction) and automatic minimum monthly payments (which you'll of course override each month and pay in full) prevent the additional expenses of overdraft charges and late fees.

Naturally, you'll teach your kids to automate a portion of each paycheck into savings.

3. Spend less than you earn, thoughtfully

"Think of yourself as a small business that generates income every month, and live within your means so you have a positive net income," says Claudio Ghipsmann, a former investment banker who wrote "Making Bank: The Personal Finance Lessons They Never Taught Us in School."

This is about spending less than you earn, but it's also about making careful choices: Lease a hot sports car or buy Old Reliable? Live on your own or with a roommate? Extra dollars unwisely spent represent lost investment potential. (Remember your new best friend, compound interest?)

Prepare your kids by showing the ways you strive to save. Explain that you pack a lunch a few times a week to save $100 or more per month. Suggest they help you look online for a better auto insurance rate or cellphone plan.

Or let them watch you pay the bills, a hands-on lesson in budgeting: what's earned versus what's owed.

"Show the kids on paper: 'This is what we bring in after taxes. This is what we pay on the mortgage,'" says Sharon Lechter, the founder of the financial literacy organization Pay Your Family First and a co-author of "Three Feet from Gold."

4. Deeply dislike debt

Unfamiliar expenses -- interview suits, utility deposits, car payments -- hit hard when you're just starting out. Simply setting up housekeeping can be a shock to someone who's never bought groceries or put quarters into washing machines.

You don't want your kids to use this as an excuse to run up the credit cards. Teach them that indebtedness limits your options. (Want to go back to school, change jobs, have a baby? You can't. You've got payments to make.)

5. Shop around

Of course, we do need to buy certain things. Might as well get the best price for them. So 20-somethings should know: Don't buy the first car you test-drive. Don't sign a lease for the first apartment that strikes your fancy. Don't assume that a "sale" price is the best price for a mattress or that interview suit.

It's never been easier to find great deals or make informed choices:

  • Online price-aggregator sites like PriceGrabber and Bizrate combined with online discount codes help shoppers pay less for just about everything.
  • Social media are good for posting queries ("Anybody know an affordable auto mechanic?").
  • Consumer websites give information on the best beds or how often a particular model of car typically winds up in the shop.