Keep your cards open unless they are charging you annual fees. You want to have a good credit to debt ratio. Thats the short answer -- but to really boost your score here are some tips I've put together over the years.
I raised my score to well over 700 points fro 500 using these steps in less than a year:
1. Know and Track Your Credit Score (be sure to sign up for the free trial of your credit score monitoring listed below. It really helped my get my score up.)
2. Never Miss a Payment, Starting Today
3. Never use more than 20% of your Available Credit
4. Keep Credit Cards that Have No Annual Fees Open For as Long as Possible
5. Extend Your Credit Limit on Cards You Already Have before You Get New Ones
6. Get Credit Cards that Have CashBack Rewards to Contribute to your Balance
7. Transfer Your Balance to a Credit Card with a Lower Interest Rate and a Higher Available Credit-
You Think You Are Going to be FORCED to Pay a Bill Late Ask for an Extension or Payment Plan
9. Take out a Small Personal Loan and Repay it Over a Year
10. Ask Someone With Good Credit if They will Account Shadow you
When you're trying to build a solid credit score it's important to get a comprehensive view of what is actually effecting it.
Your Credit Score (also known as your MyFico score) is calculated with the following breakdown:
* 35% -> History of Payments
* 30% -> Debt to Credit Ratio (available credit)
* 15% -> Credit History (length of open accounts)
* 10% -> New Credit (are you expanding your credit)
* 10% -> Credit Types in Use (varied credit types from loans to credit cards)
If you excel in one area and lack in another, only fixing the areas which you lack are going to improve your score.
You can read more about these tips on my blog: How Can I Increase My Credit Score