Don’t close credit cards as you pay them off, closing credit cards you’ve paid off can lower your credit score. If you close a credit card, you have a higher percentage of debt in relationship to your remaining available credit, which can hurt your score.
Consider adding a credit card if it gives you an opportunity to transfer a balance for a year or more at little or no interest. But be careful when applying for credit cards. New credit cards can lower your credit score, especially if you make a big charge immediately.