Observe your quota limits: Most MOOs have quota limits measured in the number of objects or bytes. Limits are placed on users to ensure that the MOO does not suffer from data base "bloat."
MOOmail: @rmmail, deleting read mail. Mail can pile up quickly and drain your and the MOOs resources.
@copy vs generics: It is better to use generics than to copy an individuals verbs. If someone has a verb you would like to use, ask the person to change the verb to a generic feature object so it can be shared by all.
@audit occasionally and #recycle those objects you no longer need.
co-ownership is a quota saving feature whereby players can share many of the same objects. Consider sharing communal spaces rather than building large areas alone which will never be visited by others. The more rooms people share, the more "tiny scenery" they can hold in common.
"Tiny Scenery" is the bane of many a wizards existence. While the descriptions on yourself, your rooms, and your objects lend the reality to virtual, most wizards would prefer to see efforts put toward adding verbs to make objects more usable and interesting.
Logging: If you own a logging room, be sure to email the log and delete the log after you have determined it has arrived safely. Logs can quickly reach proportions exceeding 60k. Clearly if you have a 50k quota limit, you want to get this log off your quota.