Hilton is offering a promotion where you can earn 5,000 bonus points after you complete two stays between October 1 and December 31, 2017. The one stipulation is that you must have one of their four co-branded credit cards, it doesn’t matter if it is with American Express or Citi. You must register in advance.
This is IN ADDITION TO their double points promotion which also goes through the end of the year. If you have any upcoming stays, this is a great unexpected way to increase your Hilton balance!