For the longest time I didn't worry anything about my credit. I didn't purposely do anything to make it worse, I just didn't pay any attention to it. When I went to apply for a car last fall, I found a few things I didn't know about my credit.
I signed up for Credit Sesame just to see how well it worked. They really don't charge a thing and they send me emails with advice and reports on credit changes. I can track my score, see available and used credit and know right away if something on my report changes.
I have been using this for about a year and I have brought my score up over 100 points in that time. The report emails remind me to visit the site and see how everything is. I wouldn't remember to do it nearly as often without them. I even get emails with offers for credit cards and loans if I were interested in that. It is the perfect way to monitor and build your credit.