Depending on your child's age, he or she may be working on using a spoon, staying out of the street, or acing the SAT — all important skills. But for my money, the most underrated yet critical life skill for kids is the ability to negotiate.

Kindergarten students in Marina, Calif. (Dave Parker)

Why on earth would you teach your kids to go back and forth, push for more, and question things? You don't have to. Kids do those things naturally — and how. The trick is to channel those impulses into something useful, like making a lot of extra money over the course of their working lives just by speaking up.

Salary.com's recent case study showed a million-dollar earnings boost over a lifetime for an average-income worker who negotiates a raise every three years, compared to a worker who doesn't ask. But more than half of U.S. employees don't ask for raises at review time, even though most employers expect them to do so. Consider that for a moment. Most of us are too intimidated to ask for money our bosses expect us to request. Speaking up pays off, literally.

There's another perk for smart deal-makers: Because good negotiators know how to offer value and listen to others, they can build better workplace and personal relationships.

Beyond the individual benefits, skilled negotiators can keep our economy growing. At the moment, former Federal Reserve chair Alan Greenspan (among others) says the recent shutdown could easily happen again due to lack of compromise skills on Capitol Hill, and many analysts blame Washington's ongoing dysfunction for a drag on the overall economy.

When it comes to deal-making, there's no reason our children can't surpass their elders. Here are some age-appropriate ways to school your kids (and maybe yourself) in the art of the deal.

Age 3 to 5: Bargaining basics

What you can do: Model bargaining when it's appropriate — at garage sales, when car shopping, when you're buying or selling things on Craigslist. Let the kids watch and listen.

What they can say: "Would you take $X for it?" Preschoolers may have trouble with sharing, but they can often understand the idea of exchanging money in hand for a toy at a garage sale.

What they can learn:

  • If you ask, sometimes you get. My oldest son used the cash-offer approach to great effect at yard sales when he was small.
  • It's OK for the other person to say no. The one place his cash approach didn't work was a local thrift shop. The owner gently explained that she wouldn't take his offer on a train set because she knew she could get her asking price, and that money would help fund a preschool program for underprivileged kids.
  • There's a time and place for negotiating. My kids watched me haggle at garage sales, but only with other adults and not if the situation looked like financial distress. At the grocery store? Nope. There, as at the thrift shop, the price was the price.

Age 6 to 12: Learning the trade

What they can say: "Want to trade?" Kids this age are often obsessed with the idea of fairness and they're budding consumers learning to spot value, so it's no surprise these are the peak years for swapping cards with friends. Elementary-age children also may try to negotiate chores on their own terms and to "bribe" siblings into handing over the remote with the promise of cards, cash, or chores.

What you can do: Listen to your child's requests for a change in allowance, chore schedule, or some other negotiable item. You don't have to agree, but being open shows your child that it's worth asking.

What they can learn:

  • A good offer has value for you and the other person. Your teen may not care about Yu-Gi-Oh cards, but if her little sister offers to spot her some chores in exchange for time on the gaming PC, they're likely to reach an agreement.
  • Whining is not negotiating. As much as I encourage my kids to negotiate, some things are off-limits. Tell your kids up front when your expectations are not negotiable and when the talks are closed. That draws a bright line and teaches kids to respect others' boundaries — as long as you stick to your word.
  • It's easy to get carried away. Your child may regret trading away that mint card with 300 damage points in the heat of haggling with pals. But it's better to learn the symptoms of deal fever now rather than at age 30 when the stakes are higher.

Age 12 and up: Looking long-term

What you can do: Reinforce the lessons they've learned, keep listening, and hold your kids accountable for the deals they make.

What they can say: "Let me take some time to think this over." This handy phrase is two tools in one. It can cool off a case of deal fever to prevent buyer's remorse, and it's an effective way to negotiate a higher starting salary or better purchase price without asking.

What they can learn:

  • You're more likely to reach a deal when you really understand what matters to the other person. This goes beyond general offers of chores or cash. When you know what a potential boss is looking for — a stock boy who's willing to work Saturday mornings, a dog walker who also cleans up the yard — you can build a mutually beneficial relationship and earn more money.
  • When you make a deal, keep your promise. People who don't follow through find that no one will negotiate with them -- and they may get grounded by Mom and Dad.
  • You can't win 'em all. Sometimes there's no compromise, and you have to decide whether to cooperate or gum up the works. (See: Congress and the shutdown.) Coming away from a negotiation empty-handed can be frustrating. Limit the pain by conducting yourself well. Act out and you can weaken your position in future bargaining sessions.

Teaching these skills to your children takes time and patience, but the potential payoff is huge, both in financial and personal terms. And if some of this generation grows up to master the fine art of reasonable political negotiation, then so much the better.