Lucky of One Mile at a Time, has a post about transferring points within the American Express Membership Rewards (AMEX MR), Chase Ultimate Rewards (UR), and Starwood Preferred Guest (SPG) programs. A good read to understand what you can and can’t do with the points in each of those programs.
Those are honestly the three favorite programs among the miles blogs, so I would expect everyone doing this to have a credit card that earns in at least one of those programs, and preferably two or all three of them. Having points in all 3 not only gives you the best opportunity to take advantage of credit card signup bonuses, but lets you have options for getting points/redemptions in the majority of loyalty programs that exist.
Also, on the credit card front, the American Express Platinum (and business version) or Premier Rewards Gold (and business version) card will get you started in AMEX MR. The Chase Sapphire Preferred or Chase Ink Bold will get you going in Chase UR. And finally, for SPG, you’ve got the American Express Starwood Preferred Guest card (there’s also a business version).
Note: Gary of View from the Wing has given me permission to use his credit card referral links, as I have explained on the credit card offers page. Thus, he will earn a commission if you apply through these links. Before applying, do make sure that these are the best offers available.