The times I've done this I've done so without trying, but I actually got up and meandered about. The first time I felt something on my face and I looked down, very groggy and saw myself lying on the bed and the side of my face was on the ceiling - how I could "feel" this is a mystery to me but I know what I saw. It startled me and suddenly there was a soft "thump" and I was back in my body and sitting straight up in bed.
The other time I woke up from my bedroom and heard the tv on in the living room next to me. I got up to see if my young son was awake and up by himself he was only 2 at the time. I walked into the living room and saw my son with a glowing halo around him watching tv and he looked over at me and smiled and then I looked at the sofa behind him and he was sleeping on the sofa too. I thought oh ok I must be dreaming this and turned to walk back to my bed .... when I got to my bed, my body was lying there and I realized I had just walked through my closed bedroom door to return to my body lol. I sat down on the bed and was back in my body and then woke up and actually went into the living room where the TV had been left on because dad and son had fallen asleep watching a movie. The experience was wild, but very unnerving too and I didn't go out seeking the experience, but I have done it several times.
As for a common denominator, I would think perhaps some form of meditation at night may help. I was actively meditating in the evenings back when these events happened. Perhaps that kind of helps the process along by making your mind more receptive and open to experiences outside the body.