Your payment history is the biggest factor in determining your credit score. Lenders don't want to give money to someone who has a history of missed payments.

Paying a bill more than 30 days late can drag down your score. "One single missed payment can drop your score anywhere from 100 to 300 points," said McClary.

If you went through a period of time where money was tight and you were late with some payments, it's time to right the ship. Curb your spending and start a track record of paying your bills on time.

Here's the golden rule: Only charge what you can afford to pay every month in full.

Keeping your balances low will help boost your credit score. Aim to keep your debt utilization — which is amount of available credit you actually use — as low as possible.

"You never want the balance to be more than 30% of the credit limit — that is, any one card or in total," said Griffin.

If you are carrying a balance on any of your credit cards, create a plan to get them paid off as soon as possible.

There's no need to have a wallet full of credit cards, but having one or two that you use responsibly will help your score.

"You should apply for credit when you need it and know how you are going to repay it," said Griffin.

But if you don't have a credit card, he recommended opening an account and making a small purchase each month and paying it off. "Credit cards have a little more weight than installment loans because you decide how much to charge and pay," he explained.

Good credit scores don't just happen overnight.

For instance, the positive effects of opening and making on-time payments on a credit card could take a few months to show in on your score, according to Griffin.

Correction: An earlier version of this story stated that paying a bill a few days late could hurt your credit score. A payment would usually need to be more than 30 days late before being reported to the credit bureaus.