A big no-no is remembering large portions and leaving them until later to write down (if you keep a notebook). It is highly likely you'll forget it all. One day I will get a voice recorder, because I've forgotten portions of dreams even while I was writing them down.
Oh man, I'm so guilty of both of those. I've had very vivid dreams and woken up mid night thinking "I'll write them down in the morning" ... yeah, that usually fails miserably. I've also forgotten dreams while writing them "And then I ... wait ... OH NO!" On the flip side, I've also remembered segways between dreams and been able to dig back pretty deep. (sometimes out of order). I'll have to try the affirmation thing. I admit I've been totally lax on that.

Have you ever been in a dream scenario, and know you've been there before, and know things about that situation that you don't know in waking life? This (IMO) is an indication that when you are 'in dreamscape', you are indeed experiencing life at a different frequency (for want of a better term), where time and space work differently, but exist nonetheless, and sometimes dreams are not just 'processing', they are living, like we do in the physical.
I'm not quite sure what you're getting at. Are you saying something along the lines of "even though I know I just got up and got a drink of water, I don't remember the exact details of the hall, refrigerator, or glass even thought they are there". Or are you refering to more of a "I had a dream, it's gone, but if I return to that dreamscape, I will remember it"?

If you mean the latter, you remind me of something curious. I've had a specific dream maybe twice in my life. It's night, and I'm on the side of a mountian in sort of an uncovered crevace. there's always a deep snow. The night sky is completely clear and the moonlight reflects brightly off the snow. I'm lying in the snow, totally relaxed. A light overtakes me and the sense of peace is just indescribeable. Since I've had that dream, every dream involving skiing or snowy mountains triggers this crazy response of "I GOTTA FIND THAT SPOT!", but while I'm awake, I've never skiied and actually kinda dislike snow.