Don't put all your efforts into getting good survey results. Many of them really don't do well in measuring guest satisfaction. Choices like "exceeded expectations" will be totally different from someone staying at at FS Marriott vs a Fairfield Inn just as much as someone at the property for the first time vs their 20th time. Once you get use to a high level of service, you can't get a high mark since I got great service as I expected.

Instead, I'd suggest promote guests to post reviews here on FT or TripAdvisor or some such site where they can verbalize their experience. Then great service can be earned every time.