Choosing the right frequent flier credit card

Q. We plan on taking a family vacation to Europe next year. Since there will be six of us flying, I plan on using a credit card to rack up extra miles. I currently have Delta and American Airlines card, but even with the added miles from this vacation, I think I have a ways to go before getting enough for a free ticket. Plus some of the better fares I'm seeing these days are on other airlines. Is there a particular credit card you recommend?

A. For a little guidance, check out our previous Q&As on frequent flyer cards here.