NEW YORK (MainStreet) -- Keith Metz-Porozni, a 31-year-old media relations professional based in Portland, Ore, had an 800 FICO credit score, which puts him in a rare, high-credit score category among Millennials.

"I really only have a middling income," Metz-Porozni says. "But I have a plan." Specifically, he measures how much cash leaves his bank account every month, "even if it's just a rough estimate," Metz-Porozni says. "If you don't know how your cash flow is affected month-to-month, you have no hope to save money or understand if you really can afford that new car or that bigger apartment," he adds. 

Metz-Porozni is an anomaly among younger Americans when it comes to having good credit. The fact is, most of his contemporaries don't.

According to fresh data from Experian, U.S. Millennials have the lowest average credit scores among any nationwide demographic, at a 625 VantageScore. Generation X averages a 650 VantageScore, while Baby Boomers average a 709 VantageScore. (VantageScore, like FICO, is a firm that uses its own formula to calculate a consumer's credit score based on data from Experian, Equifax and TransUnion, the three American credit bureaus.)  

That flagging of Gen Y credit is significant, as Millennials recently passed the venerable Baby Boomers (at 77 million strong) as the largest segment of the U.S. population. As Experian puts it in a statement, "this digitally independent generation is still much less savvy than older generations when it comes to their finances and credit management."

For Millennials, the recipe for success is a heavy dose of financial learning, experts say. "Given the significance Millennials play in financial services and the credit marketplace, it is crucial to understand this influential consumer segment and how they use credit as a tool," notes Michele Raneri, vice president of analytics and business development at Experian. "While this generation may not look like they are on the right track financially, it's important to keep in mind that credit scores are built on credit experiences, and while this generation has been slower to use credit, they have plenty of opportunities to build a positive credit history. The best way to do that is to understand credit before using it."

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That also means starting early on a path to a healthy credit score. "You need to build a good credit score when you're young - even if you don't see yourself taking out big loans -- for a house, car, etc. -- for years," says Lee Gimpel, the co-developer of The Good Credit Game, a curriculum kit for financial educators who teach classes about credit reports, credit scores and credit cards. "That's because a good credit score is largely based on having a track record of using credit responsibly. If you have five years of good credit, it's better than five months."

Consequently, Millennials are better off getting a credit card today and using it versus waiting for years until right before they want to buy a house or car, Gimpel adds. A "starter credit card" is a great place to start - think store credit cards or secured credit cards, he says.

Robert Farrington, founder of The College Investor, in El Cajon, Calif., says the best thing that Millennials can do to help boost their credit score is simply getting organized. "Too many Millennials are late on their payments or forget to pay a bill altogether, because they don't keep track of all their accounts in one place," Farrington says. "After college, Millennials could have multiple student loans, a credit card, rent, utilities, and more to keep track of. Having a good system in place to organize their finances and pay their bills is what will help save -- and later improve -- their credit score."

Farrington recommends setting up an account at a free service like Mint or Personal Capital to organize all their accounts. "Having everything in one place is the start," he adds.

College loans need to be managed better too, if younger Americans are going to build stronger credit. "Student loans are a big cause of Millennials' credit troubles," says Joe Orsolini, a Certified Financial Planner at College Aid Planners near Chicago. "We see a lot of lives ruined by student debt," he adds. "What many graduates fail to realize is that even though they may make one student loan payment that payment represents multiple loans. A student that graduated in four years can easily have eight different loans combined in to single payment."

Orsolini says that missing or being late on a single payment will put multiple negative hits (one for each loan) on their credit report. "I tell students that when they graduate the first bill they should pay every month is their student loan payment - before rent, car, or a cellphone bill," he says. "Also, sign up to auto debit the payment, doing so not only makes certain your payment is made but it also drops your loan interest rate by 0.25%."

There's really no need to fall behind on your credit score if you're a Millennial. Just learn where you stand, keep all your bills in one place and pay them on time, and be vigilant about student loans. Do that, and watch your credit score climb upward, and take your personal finances to a new, more elite level.