First, review your credit reports (free from the link below) for any inaccuracies.
https://www.annualcreditreport.com/index.action
The following sites have information on improving/maintaining your score.
https://www.consumer.ftc.gov/articles/0152-credit-scores#improve
https://www.consumerfinance.gov/ask-cfpb/how-do-i-get-and-keep-a-good-credit-score-en-318/
