Credit scores are reflective of how well you pay your bills. Pay late, have collections, scores go down. Pay on time; keep low balances scores go up. They go down much easier then they go up. If you know why your scores are low, you probably have an idea of how to fix them. Once items are on your report legitimately, your best bet is to pay off any collections, pay all your bills on time and keep low balances.
There are services who charge fees to repair credit and some who claim they can remove legitimate items from your report, be very careful if you pursue this option. Even if they can do what is claimed legally, if you do not have the budgeting skills to earn the type of credit you need to buy a home you may end up like so many that are losing their homes today.
You are entitled to a copy of your credit from each agency once a year. You should go to Experian.com, Equifax.com and Transunion.com for these and not the services who offer a free credit report and sign you up for a service with a monthly fee.
Once you have a copy you can understand why your scores are low and how you might improve. If you need help with a budget, look for a community organization or a church that offers budget training.
I hope you can get things going well for you.