In a game I want to keep things short. This post has grown out of a number of posts on the topic. 
Descriptions: From my personal experience, I don’t like DMs who spend a lot of time on descriptions. We are not published authors. Our prose will never be good enough. I’m sitting at the table to do, not to “read.” When the DM spends more than a few sentences on the amazing sights, and there’s nothing we can do about it, then… “Let’s move!”
Introductions: I don’t like players who introduce their characters talking about the color of their cloak and the exact boots their wear. This is not Creative Writing class. I try to say it all in one or two sentences. Here are two examples:
Thorhall: My character has a helmet on, a longspear in his hand, a warhammer dangling from his belt, a dagger in his boot, a huge backpack with a longsword and a shield strapped to it, pouches, dangling stuff, maps, and various pieces of armor. What a mess! Rhysalis Eina: She wears a chainshirt and carries a polearm. Her tan face is stern and her brown hair is tied into a tight bun.
Scenes: Eliminate pseudo-choice. Avoid situations where there is one correct solution and the players have to guess it. Assume that players make sane choices and move on. Example: There’s a village, or a door, or whatever, how do you want to approach it? There’s not enough information to make a rational choice. Just skip ahead until something important comes up. Once something dangerous happens, it’s time to sync mental images. This can be difficult. You think all characters are in the room, most players feel they would have never entered the small room. It’s better to ask a question instead: “Ok, so who’s in the room after a minute?”
Make every single word count. Focus on “What do you do?” instead of “And this is what you see…”