95% of your dream in lost in the first 5 minutes of waking. most people who claim to not dream do, they just cannot remember it. sometimes certain foods [like fruit or cheese] and smells [like peppermint] before bed can effect a persons dreams. myself cheese gives me horrific nightmares, where my friend have extremely vivid dreams.
keep a dream journal by your bed, when you wake up, the very first thing you should do is write/draw everything you can remember from the dream. as time goes on, you'll be able to remember more, you will gain more vivid, insightful, dreams. we tend to have 5 dreams a night, people who become really skilled with dreams will awaken after each dream is finished.
the day of the dream you cannot remember, try meditating, thinking about the dream, try and look into your subconscious to find it.