When writing my books I enjoyed getting in the mood, or being in the mood. When reading Lord of the Rings in my late teens, I loved listening to mood music. My favorites were Mike Oldfield's Ommadawn, Tubular Bells and Hergest Ridge. For some reason these captured Tolkien's tales beautifully and even today, when I hear these albums, I remember scenes from Lord of the Rings.
Writing was the same, and listening to Enjya, as example, sent me into the world I had created. It was like slipping on a comfortable jumper, my mood immediately turned to inhospitable lands, tall tales and heroism.
I also wrote on journeys and mainly trains. Something about a train helped me slip into other worlds. Whether it was the rocking of the train, the rhythm of the wheels or escaping the boredom of the journey, I am not sure. But again I found it very easy to write in these conditions. Unfortunately, I wrote on paper and when my manuscripts were completed my poor wife had to transfer this work onto a PC. My most creative moments came when driving. Not having a pencil and paper forced me to consider plots at great length. My Eureka moments often came in cars.
It is so important being able to slip into the mood for both writing and being in your own plot line. Make sure your PC/laptop is in a comfortable spot. The lighting needs to be good. The chair comfortable and a fresh cup of tea or coffee at your side. Go light on cake and biscuits though as sitting still doesn't help to burn calories. Music is a great help, but softly and in the background.
Once set, let free the brakes of life's drudgery and let slip the launch of your imagination. Great stuff.