Man... while flying is an obvious way to tell youre dremaing, for me it costs a lot of energy... like... whenever im lucid dreaming and i try to fly, i must concentrate hard in it, and usually my flights dont last much... soon i lose speed and usually stop of dreaming, or the dream change and im not able of being lucid anymore.
But i have a far less consuming way to tell for sure when im dreaming... i noticed when im dreaming everything that is "solid" is not actually solid. When im dreaming, if i press hard my hand against an wall, with some effort my hand enters the wall, like if it were made of some maleable material... and usually it lefts a hole where it entered.
Also, this is only an way to confirm that im actually dreaming. But the "feeling" one gets when lucid dreaming is different of when awake. For me it feels like if i were able to feel my sleeping physical body, to feel that its immobile, numb and confortable... like if the only physical sensation i got were one of confort and relaxement... and yet im dreaming. Its very hard to describe it. Anyway, its a recognizable thing, and whenever i feel this way i know im dreaming, and if i have any doubt i just stick my hand into some wall to make sure im dreaming.
BTW i dont know if weed helps me with lucid dreaming... when i smoke some indica i usually sleep deeply and cant remember any dreams... and when i smoke some sativa i become restless... if i try to relax, my body (mainly my legs and toes) twitch... yet im sure that smoking helped me to be aware im dreaming, cause for me being high is somewhat similar to be lucid dreaming, so after i learned how to control myself even when stoned out of my mind i also could control my dreams far better.
"Everything we do, everything we are, rests on our personal power. If we have enough of it, one word uttered to us might be sufficient to change the course of our lives. But if we don't have enough personal power, the most magnificent piece of wisdom can be revealed to us and that revelation won't make a damn bit of difference." Don Juan Matus - Tales of Power