false awakenings are pretty tricky sometimes! i can't explain it. but i usually just "know" i'm dreaming. Usually in my false awakenings I "wake up" in the wrong place (usually the house I grew up in) so I realize that I don't live there anymore and that I must be dreaming. Also, when I have false awakenings that occur where I am sleeping, many times there will be things that are off... larger rooms. objects are just strange. whatever it may be... I am not sure what to tell you because I don't know what your dreams are like.. but start questioning reality more?
I'm starting to think that ALL dreams start as false awakenings... but really.. who knows? the beginnings of dreams are the hardest to remember! (for me at least)
I think that you are on the right track though! Asking yourself "How did I get here?" is a great method.