I would begin working on improving your credit score. Here are some easy ways to work on that:
1. Work on paying off any credit cards that you have. Once those are low, keep them low.
2. Offer to pay off your debt/loans upfront; you can often pay less than is owed if you're able/willing to do this.
3. Pay all bills on time.
4. Get any potential errors fixed.
To check your credit score, go to annualcreditreport.com. The major companies are required to provide you with free credit reports once every 12 months.
If you still have problems renting, check with family a friends who may give a personal recommendation to someone that you can rent from. Admit any past problems that you've had to a potential landlord immediately and explain any extenuating circumstances in a letter. Being upfront makes you seem much more trustworthy. If you can, offer to pay several months of rent upfront. Find a co-signer. If you have a friend or family member who is willing to co-sign on a lease, this could help you tremendously.