If I have difficulty remembering dreams on waking I have found the following technique works most of the time :

I sit up in my bed with my eyes open and move my eyes from side to side. I keep my head still but look up to the top left corner for a second or two. Then look up at the top right corner for a second or two and continue until some image or trigger from the dream jumps into my head. It usually works quite well and I only need to do it for 30 seconds at most. Once I have found an anchor to the dream and start writing it down the rest falls into place.  This works for remembering other things and not only dreams.

Sometimes however if this doesnt work and I have no recollection of the dream I find that the memory of the dream is sometimes triggered through the day by something someone says or something I see triggering a feeling of Déjà vu.