This is directly from the Dream Team: There will always be two of them together, at least one of them will be wearing a white vest. If you see them, approach them, because some of the dreams require you coming up to them. On some of the dreams, shortly before they will be notified of the exact location where to go to give out the dream, and they will have to document the event by taking pictures of the specific person and a picture of the time on the watch they are given to wear. They are not allowed to wear their personal watch or carry a cell phone or other device, so that it is completely fair and they are not able to call family or friends and let them know where they will be. For example, with the Dream Suite, if it's a two-person ride, they are instructed as to which of the two people wins the night in the suite, i.e., the outside rider. I know this for a fact because my son and I were riding on Mr. Toad, and I won a night in the Dream Suite because I was the one on the outside. It's that precise.
Also another thing I learned is they give out dreams everyday until 5 p.m. So if you see white-vested CMs, say hello. There's a lot of other dreams besides the Fastpasses and the ears. There's lots of trips, cruises, even 40+ years of vacation ownership at the WDW resorts.