Rough sketches and blurry images, regardless of whether Im DMing or playing. Obviously if Im DMing I usually have a better grasp of things to better visualize positions and images of the surroundings. That doesnt necessarily mean I can always convey it any better. Reminds me of a funny story. I can't remember if it was a pre-published adventure or one I had written but I was DMing and the PCs were exploring a room in a wizards lab. We were playing TotME at the time. I think it was one of the Undermountain modules that came out later 90s. I forgot to mention that the bed in the room was a canopy bed, (which had a magical sword on top of it) just because in my minds eye I was only picturing bits and pieces instead of more realistic and complete detail. 3/4 of the way through the encounter and them exploring the room I said, "BTW, there's a canopy on this bed". They all said well that changes everything had we known that the encounter would have played out quite differently. So, for years after anytime the players and DM were picturing things differently someone would say, "Canopy Bed".