Write down everything you know about your dreams right after you get up. So really every little detail you know, even if it seems unnecessary to you. (what people you saw,what emotions you had, what objects you saw and what colors, what you felt and smelled, whether you knew the place in the dream...just everything)

I went through my past dreams several times a day in my head.
With the time I could then write down more and more and remember my dreams as if I really had these situations in reality. I was able to reconstruct it clearly and perfectly in my head.