Most reliable: I don't have much experience as I haven't had enough LDs yet, but when I used to, just realizing I was dreaming by looking around me very rarely failed.

Least reliable/incorrect reading: I failed to realize I was dreaming because I tried to open my closet with my mind and failed, then tried to look under my bed and see if anyone was under there. Because these things didn't work, I falsely concluded I wasn't dreaming. I don't know what I was thinking in the dream. That isn't a RC I've even considered doing in real life.