Eric is finally catching on!! Hooray!! I did a thread like this a few years back and everyone seemed scared of the idea of using credit cards.
The most effective way to do this is to churn and burn them. Open them up, put all your spending on them to hit the bonus, then close the card and do it with a new one.
Right now I'm working on a Citi American Airlines Executive card. 20k spend for 150k miles. Offer is from a few months ago might no longer be valid.
Last few turns I did:
Citi American Airlines - 50k miles - 3k spend
Chase Marriott - 80k points - 3k Spend
Amex Hilton - 50k points - 1k spend
2 Chase Southwest cards - 50k miles each - 2k spend and 3k spend
Barclays Lufthansa card - 50k miles
Barclays US Airways - 35k miles - 1k spend (these will be merging into AA miles soon)
US Bank Club Carlson - 85k points - 2.5k spend
My planned next cards are:
Chase British Airlines - 50k miles
Carclays Frontier - 40k miles
Bank of America Asiania Airlines - 38k miles
Some extra perks: When you hit 110,000 miles on southwest in a calendar year, you get a free companion pass for that year and the following (meaning every ticket you buy your get a second of the same itinerary free). You get 100,000 points through the card and then just buy the 10,000 more and you are there. Do it in January of 2015 and the pass is valid until Dec 2016. And southwest flights are like 4k one way so 110,000 points is a ton of flights. Great for domestic.
Miles are the greatest thing ever. I stay in fancy hotels wherever I travel and fly first class on long trips and I never pay a dime. Probably saved me 3-5K just in the last few months in Asia. All for spending I would do anyway. Plus your credit score will be perfect if you have 10+ lines of credit up to $100,000.