Promotion Details:

• Members can choose between either earning Double HHonors Points or Double Airline Miles for qualified hotel stays completed between March 1 and May 31, 2015, at participating properties.
• To participate in the Double Your HHonors promotion, members must register before checking out of their stay, now through May 31, 2015, at www.HHonors.com/Double.
• During registration, members will need to select to earn either Double Points or Double Miles for the duration of the promotion.
• To earn Double Miles, members must have selected “Points and Miles” as their MyWay Earning Style preference, and must have their preferred airline partner selected.
• Terms & Conditions for this promotion can be found at www.HHonors.com/Double.

 

Unfortunately the list of non-participating hotels is blank. This is the page quoted as having the list. The Hilton rep on Flyertalk states that these will be available tomorrow. You can register today.

Once you have chosen your option you cannot change it I am afraid.

Quick Tip: To maximize your earnings on every stay, be sure to select Points & Points as your preferred My Way™ Earning Style option in your HHonors account preferences.