Your Social Security number is the master key to your financial life. With it, a scammer can open new credit cards, take out loans, or get a phone plan in your name—all without you knowing. This is called identity theft. Only give this number when absolutely necessary, like for a job application, a tax form, or a legitimate loan you applied for yourself. Question anyone else who asks for it.

Two main things happen. First, each application puts a small, temporary ding on your score. Second, if you do get new cards, the average age of all your accounts gets younger, which also can lower your score. Your score likes to see a long, stable history. Opening several new accounts quickly makes your history look new and unstable.

A secured loan can help your credit score by showing you can handle debt responsibly. When you make every payment on time and in full, that positive activity gets reported to the credit bureaus. This builds a strong payment history, which is the biggest factor in your credit score. Think of it as practice with training wheels—the loan is safer for the lender because of your collateral, and you get a chance to prove you’re trustworthy with credit, which helps your score grow over time.

Missing a payment is one of the worst things you can do for your credit with a car loan. Even one late payment can seriously hurt your score and will stay on your credit report for seven years. The lender may also charge you late fees. It tells future lenders that you might not be reliable. Always set up reminders or automatic payments to make sure you never miss a due date.