"The credit score is going to take the one account you've had for 20 years, 240 months and the five accounts that you've had for one year. That's five accounts times 12 months and it would then average all of those accounts together so it only looks like you've had credit for four years," she says.

Also, applying for credit causes a hard inquiry on your credit report. The alternative to a hard inquiry is a soft inquiry, which is what would happen if you pulled your credit report.

Inquiries aren't extremely damaging to a credit score, but multiple hard inquiries in a short period of time can raise lenders' eyebrows, due to that whole reeking-of-desperation-thing, or possibly being up to something illegal. Most banks or credit card companies try to avoid consumers in these scenarios.

However, credit scores do take smart loan shopping into account. When shopping for products such as auto loans or mortgages, consumers are not dinged for each individual auto or home loan-related inquiry within a 45-day window.

Experts recommend doing all comparison shopping within that period of time if possible to minimize credit dings.

Don't pay fines or non-credit-card bills

"These days, public institutions and municipalities will use credit to get people to pay their fines and fees. So if someone has an old library fine that they never paid it could be killing their credit score without them knowing it -- which is why it is essential to check your score regularly," Opperman says.

Other business relationships that don't normally report your good payments can turn around and bite you if you decide not to pay as agreed. Any business, from garbage collectors to cell phone companies, can turn to the dark side when it comes to getting what's owed them and that means sending your account to collections.

"Normally when you have an account with a merchant that doesn't report directly to the credit bureaus, there is a difference between positive and negative reporting. A lot of service providers don't report positive information. But the minute you do something wrong, they can outsource that debt to a collection agency who will report it," says Ulzheimer.

"If I have a Verizon cell phone and pay $79 every single month for the phone, that information is not on any of my credit reports. But if I was on a contract that required that I pay every month and I don't -- it's really only a matter of time before they send it to a collection agency and then the collection agency will report the past-due debt, or the collection debt, on my credit report," he says.