This article from Strolen’s Citadel is easily the best piece of practical advice for a DM that I’ve found. Dungeon design is difficult to get right. Despite what the swollen published modules may lead you to believe, shorter crawls are almost always better.
This particular technique is also great in that it simplifies and accelerates the design process. You can easily whip up a comprehensive and delightful dungeon crawl in less than an hour. Of course, the time involved is directly proportional to the relative crunchiness of the mechanics of your game system.
This method works so well and can be used for any game setting. I use it often, and actually kept it to my chest for more than a year so that my players wouldn’t be able to guess what I was doing. This article is absolutely essential read for anyone planning on running a campaign, and I often return to it for inspiration.