Here's the best place for free credit scores and history https://vk.cc/3tWpbx Go see what you have and figure out what can be done to improve it. Is helpful to actually see whats pulling it down and figuring out what can be fixed. Its not that hard there are many things people can do to raise it up and keep it up with small changes. Just gotta know whats making it go down in the first place.
I am not trying to suck up to Yahoo, but their finance section ROCKS! I have found a lot there and spend my lunch hours reading. As an accountant, and someone familiar with finance, the advice and information there is top-notch.
My personal recommendation to anybody attempting to build credit: Gas card. Get one and pay it off every month. For one thing you can see how much you are spending on gas, and another, it is an easy card to get and keep. I have had the same card for my entire adult life, all of 18 years, and if you read the articles below, one of the things that adds to your credit score is having a longer credit history.