Which hotel reward program should I sign up for? [closed]

Hotel reward programs are usually by family of hotel brands, while some hotels may have their own program. Given a certain hotel booking, you must be member of a program which the hotel is part.

For example, if you were to go to a Holiday Inn, then the program would be IHG (Intercontinental Hotel Group) which includes about a dozen other chains. If you do know which one you must look it up or call the hotel and ask which program they are part of.

Keep in mind that there are some agreements between airlines and hotels which certain hotels can accept the mileage program of some airlines and so if you are working towards status already with a Frequent Flyer program, you may choose that avenue.

Depends on what you care about: free nights or extras and upgrades.

You want to go with a so-called "Super Chain",i.e. a family of hotels. See https://en.wikipedia.org/wiki/List_of_chained-brand_hotels. The bigger ones are Marriott (just merged with Starwood), IHG, Hilton, Wyndham.

I'm both Marriott Gold and IHG (Intercontinental) Platinum. 20 nights will give you entry level, i.e. IHG Gold or Marriott Silver. Marriott is a bit more upscale. If you manage to get Marriott Gold, you get free access to the executive lounge which can safe a fair amount of food expenses. IHG is a little better for accumulating and using points for free hotel nights. IHG has excellent coverage in the US, but Marriott is a little better world wide.