Before building a room, ask yourself if you can envision regular scenes being played in it. A similar question is if the room is a place it is possible to have a scene in. Instead, pick specific nexus places in the generic area to build, such as a clearing where several paths meet in the forest or a particular square in the city. If you must build generic rooms, use places to put specific places in them and expect people to play at the places. Ideally, a given MUSH room should be of a size where those within it are all within the same IC playing area and can reasonably see what other people do and say.
Interesting building is nice to look at, intriguing, and easy to walk around.
It should convey the atmosphere of the place it represents while not overwhelming with text or information, and not distract through spelling errors, difficulty in navigation, or other problems. It's better to write a good description of a plain parade field than to add chromed scarecrows. This implies that would-be builders should be familiar with existing AmberMUSH building. Follow the style of aliasing exits to their abbreviations. All exits should have a desc, osucc, odrop, and succ messages.