Are you smarter than an NFL star? A lottery winner?

After finishing his shift managing a Gold's Gym in Boise, Idaho, Brad Duke pulled into a Jackson's gas station to check some numbers he had played in the Idaho State Lottery.

He'd already spotted the winning Powerball jackpot number and "some numbers looked familiar," he recalls. "I thought I had won $1,000, maybe $5,000. The girl behind the counter ran the numbers, and usually when you win there's this little 'We're in the Money' jingle that plays. There was no jingle, and after a few seconds the girl started screaming and jumping around."

He panicked, grabbed the ticket, and bolted, forgetting to pay for his gas. As he pulled out, news trucks were pulling in. He had won $220.3 million.

Panic isn't the first thing that most people might feel after coming into sudden money, whether through winnings, an inheritance, or a big sports contract. But maybe it should be. While there are strategies to turn sudden riches into lasting wealth, the landscape is littered with people who lost their way among the trappings of affluence and requests from friends and family.

The National Football League's most recent tale of woe is Mark Brunell, a Pro Bowl quarterback who earned $50 million in his career. In 2010, he filed for bankruptcy, citing $25 million in debt from bad business deals. It's a common problem for pro athletes. The average pro football player earns a median $845,252 a year in a career that lasts 3.5 years, according to the league and the NFL Players Association (NFLPA). Just two years into retirement, by some estimates, 8 in 10 former NFL players are either bankrupt, jobless, or divorced (which creates its own financial burden). Pros in other major sports face similar problems.

"More times than not, you look at this young guy, and at the end of this ride he's broke or divorced," says Frederick Hubler, president of Creative Capital Wealth Management Group in Phoenixville, Pa., and one of 257 financial consultants registered with the NFLPA. "It's a short earnings window, and not everyone can be a broadcaster. After they're done playing, guys are older than new applicants in other job markets, and they don't want to be at the bottom of the mountain."

It's no picnic for many lottery winners, either. Take Jack Whittaker, the West Virginia man who won a $315 million Powerball jackpot in 2002 ($114 million after taxes). By 2007, it was gone. Alex Toth, who won $13 million from the Florida lottery in 1990, was broke and charged with filing fake tax returns by the time of his death in 2008.

Why is a windfall so difficult to keep? Sudden money is rarely a solution to preexisting financial trouble. Florida lottery winners facing bankruptcy before winning big were just as likely to be facing bankruptcy again three to five years later, according to a 2009 study. Then there are the emotional challenges associated with trying to maintain the rush of happiness that comes from sudden money.

"Let's say you come into money and you decide to buy a Porsche," says Dan Ariely, a professor of behavioral economics at Duke University in Durham, N.C., and author of "Predictably Irrational: The Hidden Forces That Shape Our Decisions." "The first day of driving a Porsche is fantastic, but then you've gotten used to it and it's not as good. You get tired of owning a Porsche, so you renovate the countertops. But the happiness always goes back to its original level. So we keep buying and buying to get that original level of happiness."

Then there's the pressure to help out family and friends. Newly wealthy people often have an "inability to say no to family, friends, and cousins," Mr. Hubler says. "There's a feeling of guilt for the person who has all the money."

Mr. Duke was well aware of such pitfalls when he won the lottery in 2005, so he set in motion a plan to grow his wealth. Here are six steps for anyone who comes into a windfall, even a modest one:

1. Pay down debts. As his first step, Duke paid down $25,000 worth of student loans, a bit of credit-card debt, and his mortgage: "50 percent of it should go towards servicing debt, and the rest of it towards growing long-term goals," he says.

2. Let a team (not an individual) invest. "You want multiple people not working under the same umbrella," Hubler says. "Be leery of agents who do everything, because there are no checks and balances." Hubler also suggests using financial advisers who charge a flat fee rather than a commission.

3. Space out your spending. Until two years ago, Duke kept working part time for Gold's Gym, lived in his pre-Powerball-win house, and drove a used car. "Buy a house one year, then the car the next, then the new wardrobe," Mr. Ariely says. "That way, you don't use your happiness all up at once."

4. Be kind but inflexible with family and friends. One option is to have a go-to outsider fielding all financial requests. "I'm the person the brother-in-law talks to with the idea to put the movie theater in the carwash, or whatever stupid idea," Hubler says.

Ariely advocates allocating a fixed amount of money to give away, and putting it into a separate bank account. "When it runs out, it runs out," he says, "and it's not personal."

5. A flashy investment is a bad investment. "Players like to see the money – a car, art, a new business – rather than a well-managed portfolio," Hubler says. His firm tries to steer clients toward annuities specifically designed for people who get a large lump sum. "Those programs are like forced savings accounts – like putting $500 under the Monopoly board so you can't see it until you want to buy Boardwalk," he says.

6. Set aside 'fun' money. It's OK to have a little fun with newfound wealth. Duke allowed himself one big splurge: bicycles. "It's sort of embarrassing, but I spent $100,000 on cycling equipment," he laughs. Still, he only allows himself 2.5 percent of his income for "discretionary spending."