Hey Alex, congrats on the LD!

Sometimes after I wake up I try all those suggestions above (check list, laying still, fragments etc etc) and I still can't seem to remember anything. What usually helps me is opening up a word file, taking 5-10 minutes and writing out a pure stream of consciousness style block of text. I initially keep the topic related to dreaming but allow my mind to wander as I continue writing. The important things are to write/type as fast as possible, don't censor yourself (ignore spelling and grammar), stay positive and remain receptive.

Example of how I might start: "I know that I have dreams evry night and I allow myself to remembr them...rememberingg dreams is easy and as i open mind the dreams are bound to come flowing back. maybe it was about soccer or maybe school...its easy to remember dreams...people talk about their dreams all the time... like Tina was telling me about..." blah blah blah

Eventually some tiny thing triggers an avalanche of recall.

I've noticed the same thing as you about the loss of vivid imagery and general epicness of a lucid dream upon waking after thinking "everything looks so real!" in the dream itself. For me, if a random lucid dream coincides with a period of slumping recall, the after-effect of the dream is not as potent. By contrast, if a lucid dream happens during a period of soaring recall, then the euphoria and memory of it tend to stay with me much longer. I wonder if it could be peaks and valleys in brain chemistry.

Good luck for big recall and many more LDs