I don't subscribe to the idea that you need credit the way everyone thinks you need it. The only reason to need a credit score is if you need to buy something... on credit. Essentially, you are building a debt score so you can do a better job of putting yourself in debt. If I pay for everything in cash, I don't need a credit score. However, most of us don't have the wad to outright buy a house.
Personally, I buy near everything on debit or credit card WITH the impetus that I have the full amount sitting in the bank that I can pay it off immediately. In this sense, I'm using the cards as a way to just not carry around paper money. I pay the credit card in full each month, and I never carry a balance. EVER. As a side benefit, I get some cash back, which, since I am paying off in full each month, actually counts as cash back - not an incentive to use a card where I get a dollar and lose five