The 2 most important money rules to follow in your 20s, according to a bestselling author who's written about finance for nearly 3 decades

Your 20s are a time for living it up. But if you're the type who tends to get a little too reckless when it comes to spending money, you'd be wise to establish some simple ground rules now. No doubt you'll thank yourself later.

In a recent Facebook Live interview with Business Insider, personal finance writer Beth Kobliner laid out the two most important things to do financially in your 20s.

An updated version of Kobliner's bestseller "Get a Financial Life: Personal Finance In Your Twenties and Thirties" will be released in April, and her new book, "Make Your Kid a Money Genius (Even If You're Not): A Parents' Guide for Kids 3 to 23," is available now.

Here are her hard and fast rules for managing your money as a 20-something:

Don't fall into credit card debt

Though not all debt is bad - student, home, and auto loan debt, for example, could help you get ahead financially - credit card debt can ruin your credit score and affect your job, insurance, and real estate prospects for years to come.

"Basically, in your 20s, you want to not get into credit card debt," Kobliner told Business Insider. "Because remember, if you put something on a credit card that's charging you 18% [interest], that is the equivalent of earning 18% if you pay it off. But if you're paying out 18%, you're losing a lot of money every month," she said.But if you do find yourself slipping into the trenches of debt after an ill-advised shopping spree (or three) or an unexpected medical emergency that your savings wasn't equipped to cover, pay it off as soon as possible, Kobliner says.Check out her handy debt-repayment chart to figure out how the number of monthly payments you'll need to kill your debt based on how much you're paying each month and your interest rate.

Save for retirement

Research shows that while millennials expect to fund their retirement largely through savings and investments, only 42% of millennials have actually started saving. It may seems eons away now, but the only way you're going to live comfortably in retirement is by preparing ahead of time.

"Put money in a Roth IRA ... that is a simple thing to do as much as you can," Kobliner says, adding that you don't even have to contribute a ton of money, because as long as you start early, compound interest will take over. And if your company offers a 401(k) plan, take advantage of it. In some cases, employers will even offer a contribution match - free money."I wrote the first version of my book 'Get a Financial Life' 20 years ago, and I have people coming over to me now in their late 50s, early 60s, saying 'You know what, I listened to you and now I have a pile of money,'" she said. "So definitely do that."

Check out Business Insider's full Facebook Live interview with Kobliner:

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