If you use credit cards in a intentional way, you can free up some valuable perks. We geek out on strategies to make credit cards work for you, without getting out of control on spending. Here's what to remember:- Use credit cards that have the best rewards on the things you spend the most money on.- Protect your credit score: Always pay off your balance, don't spend more than 30 percent of your limit, don't cancel a card you've had for a long time.- Don't outgame yourself by accepting too many new cards with sign-up bonuses.- Know yourself: If you've had trouble with running up debt, don't tempt yourself with more cards.