We typically recommend fixing the rate as much as possible, unless you know that you can pay off your debt during a short time period. If you think it will take you 20 years to pay off your loan, you don’t want to bet on the next 20 years of interest rates. But, if you think you will pay it off in five years, you may want to take the bet. Some providers with variable rates will cap them, which can help temper some of the risk.
The number of credit accounts you have open is also important to control. Credit cards are easy to get: Almost every store has a quick, convenient way to get you a new card. Attractive incentives, such as big discounts on purchases the day you sign up, add to the temptation. If you shop in that store often, it may be worth getting its card; otherwise, resist the urge.
If you have a high balance on a credit card and are only making minimum payments, start paying down the balance. It's important to pay down (or even better, pay off) revolving accounts such as credit cards. This will lower your credit-to-debt ratio (what you have borrowed in relation to what you could borrow), and is one way to improve your credit score. Paying off installment loans such as auto loans, student loans, etc. won't improve your credit score as dramatically.
With poor credit, you may not be able to get approved for new credit products like credit cards. Although you may still be able to take out an auto loan or a mortgage, you’ll pay a much higher interest rate because of your low credit score. Compared to a borrower with good credit, someone with poor credit can pay $50,000 more in interest on a mortgage. Over an entire lifetime, you could end up paying over $200,000 more in unnecessary interest just because of bad credit.