I travel quite a bit and am very paranoid about cameras in hotel rooms. I've seen plenty of videos so I know how small and easily hidden they can be.
The problem nowadays is that most of the tiny cams are also wireless. :Q So it's not as easy as looking for two way mirrors and pulling pictures away from the walls anymore.
Common places for hidden cams in hotel rooms:
Behind pictures and mirrors
Smoke detector
Switch plates on the walls or electrical sockets
Clocks, vases or any freestanding object
Or really ANYWHERE.
Typically they are mounted for a view of the bed and shower, so look around from that vantage point.
Years ago I actually did find a camera. It was in a drop ceiling in front of the bed. This hotel was a fleabag "no tell motel" where people rent the rooms by the hour.
Less harmful uses for these cams these days are for catching babysitters abusing your kids (as happened last week as seen on CNN).
But back OT: I've never caught anything from a hotel seat b/c unless I'm staying there for a few days, I always cover the seat w/paper. I don't drink out of any glass that wasnt' sealed in plastic and even then I wash it first.