A lot of people have trouble with activities that require the rapid generation of a large amount information to specific parameters. Canonically, turning on a light in a dark room is difficult for many, however I have heard from a few people that if one envisions the room in one's imagination before turning on the light, it can become much easier.

If you are interested, Stephen LaBerge and Lynne Levitan did a small study on the 'light switch' task: http://www.lucidity.com/NL52.LightandMirror.html

They got some data from a group of lucid dreamers on some dream control tasks:



From the discussion:

Quote Originally Posted by LaBerge
In the final analysis, the Tibetan Buddhist view that all dream images
are transmutable may be exactly right. If so, we wonder if it may be
possible also to learn to control the stability of these images,
creating lasting dream scenes and objects, achieving a state of virtual
reality far beyond the wildest dreams of the computer programmers.