The two biggest factors in your credit score are paying on time and managing how much of your credit limits you're using. That’s why they come first in this list of tips:
Pay all your bills, not just credit cards, on time. Late payments and accounts charged off or sent to collections will hurt your score.
Use no more than 30% of your credit limit on any card — less, if possible. The best scores go to people using 10% or less of their credit limits.
Keep accounts open and active when possible — that gives you a longer payment history and can help your "credit utilization," or how much of your limits you're using.
Avoid opening too many new accounts at once. New accounts lower your average account age and each application causes a small ding to your score. We recommend spacing credit applications about 6 months apart.