I made the mistake in the past of paying off all of my credit cards and closing them. Once you have a credit card i wouldnt close it. pay it off if you want but that dosnt really help your score. What helps your score is
Having credit for a long period of time
managing that credit wisely keeping your debt to available credit ratio high (lots of available credit and low debt)
Paying your bills on time.
Say you open a credit card once you hit 18 and at age 23 you close that card because it has a high interest rate and you open another card when you go to apply for say an auto loan it will show that you have only had credit for a short period of time because you closed the first account so it no longer counts. Even if the card sucks i would keep it open maybe go buy a burrito now and then on it to keep it active and pay it off. But what really helps your credit is only using about 20% of your available credit and manage your credit at 20% Buy a few things and pay them off frequently all while keeping your card at 20% sure its going to cost you money but youll be raising your credit score thus saving you money by getting you a lower interest rate in the future. IF you just pay off and close accounts what that is actually telling lenders is that you are not capable of handling your debt. So i say keep it open and manage it I wish someone had given me this info when i was 17/18 my credit would be amazing by now instead of just good.