Credit Advice

I think it depends on your idea of quickly and what is on your credit reports.  If there are no collections it could improve rather quickly by paying down credit cards and such. 

make every payment on time every time
keep your balances low ( under 20% of credit line)
and give it time... banks look at a rolling 36 month history...

I started off by locating a bank that does "fresh start loans". These loans are small, don't require a credit check, and report to all three credit agencies. In the past year I have increased my score 100+ points. The key is, pay the loans on time and completely. Wait a month or two in between so that the account shows "paid as agreed" and so that you don't show a NEED for the loan. I am on my third loan at the bank and just got approved for a secured credit card. My deposit is low and my credit line is around $200. What most don't realize is that, its not the amount that you borrow that impacts your credit the most, it's the number of on time payments. This is the fastest I have ever seen a credit score increase. If I can help you further, please let me know. My email is dyer.document.services@gmail.com

First make sure you get all of your bad debt paid off. THis is key in getting your credit score up. Paying these off will increase your score a bit. Next, you need some kind of active credit. If you don't have any open credit lines, get a secured credit card. They are easy to get and most report to the credit agencies. Use it as a filter (use it but pay off the balance, or keep the balance low), and you should see your credit score rise dramatically withing 3-4 months. I got a new car loan and opened a secured credit card and my score has increased almost 70 points in 3 months.