Do you pay your bills on time (discipline)?
Payment history is a major factor in credit scoring. If you have paid bills late, have collections or a bankruptcy, these events won't reflect well in your credit score, however there is light at the end of the reporting!
Do you have a long credit history (longevity)?
Generally speaking, the longer your history of holding accounts is, the more trusted you will be as a borrower.
Have you applied for credit recently?
If you have many recent inquiries this can be construed as being negative by the bureaus. Only apply for credit when you really want it.
What is your outstanding debt?
It is important to not use all of your available credit. If all of your credit cards are maxed out, your scores will reflect that you are not managing your debt wisely.
800 and Higher (Treated like Royalty)
700-799 (Very Good)
620-679 (Ok or Fair)
499 and Lower (Very Bad)