If your employer offers a 401k match, contribute at LEAST enough to get the full match. That's free money — like a 100% instant return. Skipping the match is leaving thousands of dollars on the table every single year. Do that before anything else.

The biggest financial mistake I see people make is not having an emergency fund. Before investing, before paying extra on debt, save 3-6 months of expenses in a savings account. This protects you from going into debt when unexpected things happen.

Pay off your highest-interest debt first — that's almost always credit cards at 18-22%. There's no investment that reliably beats paying off an 18% credit card. It's a guaranteed return. Knock that out before you even think about the stock market.

The simplest advice I ever got was: spend less than you earn and invest the difference. Sounds obvious but most Americans don't do it. Track every dollar you spend for a month — you'll be shocked where your money goes.

I made this exact mistake when I was younger and it cost me. Learn from others instead of learning the hard way. The personal finance section of any bookstore has dozens of books — they mostly say the same sensible things for a reason.