What’s the most effeciant way of keeping a dream journal?
Write down keywords on a notepad next to your bed each morning and write the full dream in a DJ on your computer (In this forum? 
) later on.
It depends on the person. Everyone has their own preferences.
You can write or record your dreams. Some people prefer to record them instead of writing them, but writing is the most used. (That doesn’t mean the most efficient however)
It is at least good to have a notebook next to your bed to write down something when you remember it. When you wake up in the middle of the night it is really recommended to write things down. Often you won’t remember those dreams anymore if you don’t write them down. If I were you I would write down the whole dream then and not just keywords. Sometimes keywords are enough, but I have experienced too that I wrote down keywords but forgot the context of the dream. This happens more with dreams you had and after that you have slept again. Writing down keywords is faster so in that way it could be more efficient. You can later write down the dreams fully (on computer)
Before I started a DJ here and when I just started I wrote down every dream in detail in my DJ. At least almost every dream, unless I was too lazy to write it down. It sometimes gives you more details, because you can often remember the dreams the best when you just woke up from them. But it does take some time and sometimes you don’t have it.
I wouldn’t recommend to write down nothing and think you will remember the dream anyway. It seems to be happening a lot more with me lately and I can assure you that it doesn’t do your dream recall good. You often forget a lot that you know you remembered before.