Is that no one REALLY knows. I mean, I can give you an outline of most determining factors. But, I can't tell you exactly how much one 30 day late is going to impact your credit score or how big an impact a credit card balance increase or decrease will have. The calculations behind a FICO score (or any of the other credit scores) are a closely guarded trade secret.

There are some tricks out there a lot of people are not aware of, though. For example, two guys with the exact same job and exact same credit history except guy A owes $10,000 out of $10,000 on his credit cards and guy B owes $20,000 out of $50,000. Who has the better credit score? Guy B, guy A's credit score is hurt significantly by the fact that the credit he has is all used up, even though he owes half what guy B owes. Or, that in some cases bankruptcy will actually improve a credit score because getting out from under debt makes you more able to pay new debt and there are laws regarding how frequently you can declare bankruptcy so it will not be an option to get out from under new debt.

Anyway, the advice you always hear is still the best. Pay your bills on time, don't borrow more than you can afford to repay. And, the most important one you don't hear enough: Establish a credit history! It's vital to major purchases like cars and houses that almost everyone has to get financing to buy.

.. for keeping a good credit rating. Don't buy what you can't afford! Simple! If you can't buy something without going into your overdraft or redding out your credit card, don't buy it! Exceptions are large purchases like houses, cars, etc. that, as Maverick mentioned, most people need financing to purchase. It gives you a great sense of pride to buy something you have wanted for a while simply by working for it.

good advice