Has your 0% credit card deal just come to an end? Do you have several high interest loans/credit cards to pay off?
Are you planning on buying a new car? Applying for a mortgage? Need a loan to cover cost-of-living increases? Unless you can pay for a car or house up front, all the above will require a credit check of your finances, from any potential lenders/creditors.
Before asking for credit, check your credit score! You can do this online via a credit reference agency. Need to improve your credit score?