I have worked with alot of Millennials that are just learning about what their credit score means, as well as people of all ages that went through a Foreclosure or a Short Sale after the mortgage melt down a few years back. The goal was to improve their credit score so could could prequalify for a home mortgage.
The best tool that I have found, that works for my clients, is top open a credit score tracking account with them on CreditKarma.com CreditKarma is a secure website site where you can input your Social Security Number, list all of your bank accounts, credit cards assets, liabilities etc...etc.
It's a great tool for you to learn what you have to do to improve your credit based on your specific circumstance. I have also found that most of my clients get a quick jump (25-80 points) just by finding and correcting discrepancies that were sitting on there report that they didn't know about.
There are also tutorials in the system that will teach you how to improve your credit at your own pace. The site also alerts you when there is a charge to one of your bank accounts or credit cards. Just the fact that you pay attention and comminicate with the credit bureaus helps your score.
I find that for the clients that have used CreditKarma along with the guidance of my local lender are usually qualified for a loan and in a home withing 4-6 months.
If you need a helping hand, go to me profile page and give me a call. I'll be Happy to point you in the right direction.