Love this question .. and that you found this site.
But first: I think that testimonials, and more, references, are little used or used badly by most vendors in our industry. For example, I have offered to be a reference for a great property or vendor and have never had my name given out. At the same time, when I've requested references from a vendor in the RFP process, and stated specifically that it had to be for a like-event, I've been given nothint like that.
Testimonials are tricky - I've been asked to do them often over 35 yrs. in the industry and have always said no. The reason? They often are platitudes only w/o the specifics.
SO...the long way to your original question:
- Collect different ones - for catering only or event only events v. meetings w/ guestrooms and more - and have them ready to go.
- Make sure they are current. If a testimonial is more than a 9 months old, it may be irrelevant esp if there's been a change in staff or a renovation.
- Publish them on your web site - and have a link to different kinds.
- Have them on signs in your booth at tradeshows.

I hope others will weigh in.