To my mind, there are - in science fiction and fantasy at least - three primary methods to introduce the reader to the world you make. 1. The ignorant child method. Used in David Eddings' Belgariad, with the character Garion, or Tad Williams Memory, Sorrow and Thorn character Simon. Each are ignorant of the world around them, but as they find out - so, too, does the reader. 2. Knowledgable character method. The character in the scene already knows much, and does not waste time on descriptions of what he sees, information is instead gradual, and the image you may have in your mind early on is not necessarily the image you will have when you finish Reading. Raymond E. Feist is skilled at this. 3. Reflective character method. The character may be ignorant or knowledgable, but recalls details or descriptions he may have missed the first time through, for example. Personally, I use a combination of the second and third styles. What do you use, and what are your thoughts on the methods?