Do not use direction bias. Words such as behind, in front, to the right, etc. should never be used because you never know which direction a player is facing. Use cardinal directions; north is always north. Do not assume that characters have been in this room or surrounding rooms before. For example: "This room is even colder than the surrounding chambers." If you have not been to all of the surrounding chambers, or have teleported in somehow, this would make no sense. Another common problem is "This path continues to climb steeply uphill." If you were coming from the uphill direction, would not it be climbing downhill? Do not use movement bias. This means that when writing a description, do not say "You are walking on a path" because you never know. The player could be flying, levitating, slithering, crawling, stomping, or anything in between. Do not use time or season bias. This means that when writing a description, do not say "The sun shines powerfully through the window". At night, that will not make sense. Also take into consideration all the different races and classes. Some races and classes may not need air, food, or water. Some may not have feet, clothing, eyes. Pretty much anything is possible, so know the MUD and its mortals before you start building. Try to make your area interesting for all the major character classes, not just Barbarians or mages. Build in parts where thieves and clerics have a special part to play. By the same token, do not assume all anyone wants is +damage equipment.