How do credit cards affect someone's credit score?

The credit cards are not that bad unless you don't pay for them. The things that affect your credit score negatively are too many inquiries. That means that the credit granter has asked about you to one

of the bureaus. If you have a good pay history then an inquiry might not cost you more than two points. If you have a poor pay history it might affect you by ten points. Every time you've applied for credit is a negative. The issue is whether it's a two point negative or a ten point negative.

There are things that do not impact your score. For instance, everybody gets a zillion credit card offers in the mail. Those don't impact your score because they are promotional. An account review by your creditor also does not impact your score. It simply means that you already have a relationship with the credit granter and they are just looking at you to see how you are doing. It's very random. Consumers don't get it. "You have been pre-approved" doesn't mean they've actually looked at your credit yet. If you have perfect pay record with your creditor, but you had some problems with another creditor, the first can close your account, increase your interest rate, or make a negative report on your credit report for them. That's so scary because it could be your first one. They can shut you down based on your performance with somebody else. When you ask for your own information, it has a zero impact on your score.