I do trailer checks for Certified. You don't have to hang out all day. Generally you have to watch the first showing of the day the movie is released. If the theater is showing the same movie on 5 different screens then you have to view the trailers on all 5 screens, but when they have that many screens, the movies start usually within 1/2 hour of each other. I did Ocean's 13 a couple of weeks ago and I was at the theater for 2 1/2 hours to get all 5 screens. Occasionally, you are allowed to attend any showing of the movie on a Friday or Saturday, but most of them want the very first showing.
They usually pay from $7.50 to $12.50 for the first screen and $2.50 for each additional screen. I have found it to be more to my advantage to stick to one local theater and sign up for trailers to 2 or more different movies if possible. That way you get the initial big payout twice in the same timeframes you are there.
Be careful to check the theaters listings for times first before you sign up for more than one movie though, so that you know you will have time to watch all the trailers at the, first movie before the trailers start for the second movie.
I have found (at least in my area) that they start the trailers at about the time listed as the movie showtime. Prior to that they show advertisements, but they don't count for the trailer checks. The trailers typically run 10-15 minutes, so if your second movie is scheduled to start at least 15 minutes after the first one, you should be ok to sign up for more than one.
Most of the trailer checks then want you to call in your report by phone immediately after you watch the trailers, sometimes you will have time to do that before having to get into the second theater. I like these kind of shops because I don't have to worry about going home or finding a wireless hotspot to turn in my reports, this way I can do other mystery shops or run my own errands and not have to worry about getting the reports in.
The open checks and blind checks are different, they do require you to be at the theater for several hours, and perhaps all day. Since I work my full time job 3pm to 11pm, I am not available for these types of checks, they almost always need to be done on a Friday or Saturday.
Hope this helps everyone considering these kinds of assignments.