Check if the mattress has an “allergy-free” (formerlly known as bug-free) bed cover on it. Hotel dogs walking around with sniffing dogs in the lobby are also a good indicator.
Keep in mind that the little critters are found in hotels of varying classes, including 4 and 5-star ones. Bedbugs can live without a meal for more than a year and hitch rides around the world in your luggage. Lovely.
[via Consumerist]