Do not use your credit cards. Pay for everything you buy with cash instead. Any credit card purchases should be paid in full the same month of purchase. Do not carry a balance on your cards.
Work to get all of the bad information taken off your credit report. It's important to keep a record of all correspondence, whether it's via the telephone, regular mail or email. Make sure you mail your dispute letters through certified mail, so you have ample proof that it was mailed and received.
If you are attempting to raise your credit score with the credit bureaus, but are encountering road blocks whenever you apply for new credit, then open an account with a credit union. You may find that the credit union has more options and better rates to offer you than banks will.