Cash Flows. Cards are there to aid your cash flows, not to increase it. You don’t get richer with using a card since you need to pay the balances every month anyway.
You know what’s the best deal? Purchase all items on sale (at huge discounts), then pay them via credit card 0% installment. You already got items at a bargain, you even got a financial leverage by paying in deferred monthly amortizations, at no additional hidden charge at all.
So say you were approved of a card and is excited to use it. The first thing you do is sign the back portion of the card as a security measure. Most transactions you do will require a signature that matches the signature in the credit card.