First of all, Welcome, the Elusive!
Your questions are mostly person-specific: Some find it best to sleep in a cold, dark room - while other prefer a warmer room, with a bit of light. The best way to know what is best to you is to experiment.
However - It is more likely, as far as I know, to successfuly WILD while sleeping on the back or on the side.
I used to use hand RCs, and those sometimes fail - When you are very tired, you imagine you have done your rc, and therfore “realize” you’re dreaming while being awake - Causing you to burst back into reality. Doesn’t happen to often, though.
I also prefer a completely dark room - Since I like to notice the exact moment where the HI begin, and play with them. In other words, if you see something, it isn’t really there. It also helps getting used to looking through closed eyes (Which is what I do when I dream: I look through my own eyes.), since you see the same thing while your eyes are open and while your eyes are closed.