It Takes Effort On Your Part It Takes Time It Takes Some Money
(1) In order to improve your credit, you need to deal with all of the accounts that show a bad pay history, collections, judgements, and everything that is considered derogatory. It is easier to clean up old accounts that are either paid off or that you plan to pay off. Credit repair does work, but it takes time for it to work. How long depends on how rough your credit looks.
(2) New, fresh, good credit history will bring your scores up. Every month the three repositories (Equifax- Transunion- Experian) look at your credit to see activity on accounts you have open in order to issue you a credit score. Simply fixing the bad credit isn't enough. You must give the repositories current, and active accounts that are in good standings to grade you by. You can be re-establishing new credit the same time your are cleaning up the old, bad credit. A secured credit card is a good start, but understand that not all secured credit cards report to the repositories. Also, one account will not be enough. Get two to three new active accounts. Always ask if the card you are considering reports to the three repositories. If you have friends or relatives that will put you on their credit cards as an "authorized user", their history will then appear on your credit and give the repositories a great history to raise your scores, assuming they have been in good standings. You can join a credit union. Give them $500 or even less to start a savings account for you. Once the money is in your account, ask them to grant you a small signature loan using your account as collateral. They usually will accomdate you and grant the loan. The pay history will then report to the repositories. I have seen credit reports that show little to no activity that have no credit scores (na) because there is nothing for the repositories to grade from.
(3) The sooner you act to improve credit, the sooner your report and credit will reflect your efforts. Don't just do a few things and not follow through. You credit will not fix itself. Once you feel that you have done evrything to improve your credit, the longer it stays fixed, the better your scores will be.