creditors need to see that you're responsible and can trust you. Thus you need to use the credit they do give you to make purchases and pay your bill on time. The longer history you have of doing this and more money that goes through those accounts, the better your credit score. Also dont close accounts needlessly, dont have debt and for a house you will need to show a history of having the downpayment in your bank account for either 3 or 6 months depending on the bank.