If you have Hilton Hotels (Waldorf-Astoria Collection, Conrad, Hilton, DoubleTree, Embassy Suites, Hilton Garden, Hamptons Inn, Homewood Suites, Home2) stays from October 1st to December 31st, definitely sign up for extra points. Even if you booked it with a third party website like Expedia which usually does not accrue points, still register.
If you put any incidentals like room service on those bookings, you will get double points. Make sure your Hilton HHonors number is attach to your reservation at checkin.
The link to register for the promotion – here.