GOLDEN VALLEY, Minn. -- Millennials looking to take out an auto loan or qualify for a home mortgage need to have good credit but many of them are choosing not to build their credit score through credit cards.

While a majority of older Americans own a credit card, a Bankrate Money Pulse survey found that just 33 percent of adults between the ages of 18-29 have one.

"If used responsibly, credit cards can be a great tool," said David Carlson, who runs the blog "Young Adult Money." Carlson is also the author of the book "Hustle Away Debt."

Carlson said using a credit card is the easiest way to build your credit history and lift your score. While lenders have their own standards for what is considered a good credit score, generally, a good credit score is 700 or higher. An Experian survey found that more than half of college students do not know their credit score.

Many major banks and credit card companies allow their customers to access their credit scores for free. You can request a free copy of your credit report (does not include credit scores), here.

"Missing a payment is probably one of the worst things you can do for your credit score. You're going to want to make sure that you consistently make your payments, at least the minimum but ideally you're paying off the balance every single month," Carlson said.

Carlson recommends requesting a credit limit increase every six months and keeping a balance less than 30 percent of the total limit. Even if you are not using your credit cards, if they don't have annual fees, Carlson recommends leaving them open and keeping the credit history.

If you have debt, Carlson said you should focus on that first. "That's going to help your credit score more than probably anything else you can do," he said.

For those with bad credit or no credit, Carlson is a fan of using the Self Lender credit builder loan. You take out a loan with Self Lender for $1,100. That money is put into a certificate of deposit in your name and then you make monthly payments on the loan for a year. When you are done making those payments, you get the money back. Ultimately, you end up paying about $75 in interest.

"It's only $75 and what you're really buying is a higher credit score since they're very intentional of making sure the credit bureaus know, 'Hey, this person took out this loan, they're making these payments' and it's been very effective for a lot of people," Carlson said.

For more information on credit scores, visit Carlson's website.