I have a very good credit score, as I look after it. In 2009 I first checked my credit score, it was poor something like 450:999 then I started looking after it. I had vast amount of late payments, no defaults just late payments. Which seriously affect your credit, or at least here in the UK it does. Afaik a late payment will stay on your credit score for at least 6 months, defaults last for ~ 5 years and CCJ's are ~ 10 years.
I used to withdraw all my money before debits were due as I couldn't manage my money at all. However, after looking after it for a few years my credit score is currently 990:999 which is the highest it's ever been. If you don't take action on it now, you'll sorely regret it when it comes to getting a mortgage or even finance for a vehicle. It also helps to know that you'll be accepted for the best rates on loans when your credit is excellent.
PS: a credit card can be very useful to boosting your credit score. If used correctly.
I use mine if I'm working away, I'll pay for my fuel & accommodation with it, then when I get paid it back at the end of the month, I clear my credit card. Or if I want a new TV or something, I'll buy it with the credit card, go home and clear it. This is a very easy way to boost your credit score, quickly.
However, if you use it unwisely you'll just plummet your score even more.