Credit usage is the key factor in determining your FICO (Fair Isaac & Co.) score. Characteristics are weighed according to their predictive power. Factors with the highest weights are collections, judgments, bankruptcies, late payments, current balances, too few or too many revolving accounts, finance company accounts, number of accounts opened in the past 12 months and number of credit inquiries.

FICO scoring looks at credit patterns over a period of time. In other words, one late payment will not ruin your credit score. However, a history of late payments and high credit balances can have a serious effect on your score. Here are some things to keep in mind:

• A late mortgage payment will affect your credit score more than a late credit card payment
• Outstanding credit card debt or personal lines of credit should not be more than 50 percent of the total limit
• Frequent credit inquiries drag down your score
• New mortgages which have been duly serviced for a period of at least three months can boost your rating
• Older trade lines weigh in more towards your score