I want to take my kids to Disney in 18 months. I don't have a credit card and am trying to figure out which one to get so we can save some $$$ on the trip.
Well there are cards that will pay you up to 1.5% on all your spending in general. There are also cards that will pay higher rewards percentages on some categories of spending for travel (car rentals, airline tickets, etc.). For example, the Chase BP Rewards card pays 2% back on airline tickets, hotels, vehicle rentals, and restaurants. Other cards will pay up to 3% back for your spending at restaurants and in some other categories like home improvement (e.g. the Citi Professional card). Still other cards pay up to 6% back on gas, groceries, and drug store purchases (e.g. Citi Driver's Edge). I found all these cards at the rewards calculator site here: http://www.creditcardtuneup.com/.
In general, to maximize your rewards (cash back, etc.), you'll probably want to pump all your normal spending through credit card(s) that pay the best rewards in the categories you normally spend the most. Then, just pay off your balance every month and enjoy the cash back rewards or other rewards.
To find the credit card (or combination of cards) that will pay you the most for your normal spending profile, you can use this rewards calculator:
http://www.creditcardtuneup.com/
You just plug in how much you normally spend in each of the various categories each month and it calculates how much you'll earn from the various rewards cards per year.