Here are some steps you can take:
1) If you haven't done so in the last 12 months, you can get free copies of each of your credit reports from AnnualCreditReport.com and correct any errors you may find.
2) If you have old delinquent debt that's past your state's statue of limitations and has fallen off your credit report or getting close (7 years after the last activity), you may want to leave it alone rather than making a payment that could restart the clock.
3) Put all of your remaining bills on autopayment so you don't have any late payments.
4) Work on paying down your debt. The fastest way to do this is to put extra payments towards the highest interest rate debt and then once it's paid off, put those payments towards the debt with the next highest interest rate.
5) Avoid new credit inquiries and closing old lines of credit.
6) Consider placing a security freeze on your credit reports to prevent someone from opening credit in your name.
7) Sign up for free credit monitoring and get other tips on how to improve your credit from sites like WalletHub (uses TransUnion), Credit Karma (uses Equifax and TransUnion) and Credit.com (uses Experian).
You can also learn more about managing debt and credit in our new book, What Your Financial Advisor Isn't Telling You: 10 Essential Truths You Need to Know About Your Money