Good stuff. I've started describing what I do as , "continuous vigilance", which pretty much means mindfulness I believe. Some of the main things I'm mindful of are:

+ location (my dreams are almost always in imaginary/non-waking places)
+ strange/bizarre/shocking/surprising/new things
+ interaction with people (because my vigilance usually wavers while interacting with people, and I mostly interact with people in dreams), this one's hard to keep
+ thinking about dreaming: because after all, the only time I'm not thinking about dreaming is when....I"m non-lucidly dreaming!
+ the dream feeling itself
+ gravity