Part of the enjoyment of a MUD is playing with others. A MUD with players who interact, work together, and even fight each other will better maintain its player-base than a MUD where players work solo.
Here are some ways to encourage grouping:
-Do not allow multi-playing, or limit it to 2 chars being allowed logged on at one time. If a person is able to take advantage of grouping without working with someone else, it reduces the need to work with others
-Do not reduce experience for killing a MUD when part of a group; especially when players in the group are close in level
-Make each class different, so that each char will have strengths and weaknesses.
-Do not allow, or place limits on the ability of to multi-class. A mage/cleric/warrior has less need to group than a pure cleric.
-Make sure that spells can stack to further help a team. For example, maybe give warriors 'dodge', mages 'armor', psions 'illusion', bards 'song of defense,' and clerics 'sanctuary' so that a warrior tank can receive the benefit of armor, illusion, song of defense, and sanctuary making him a much stronger tank if group with others. By allowing skills and spells of each class to make the other classes stronger, it further helps foster grouping.
-Design zones with groups in mind. Make zones where you need the skills of 3-4 different classes to clear the zone. Perhaps a door that needs picked by a thief, a strong mob in a silence zone that requires nonmagical strength, and another MOB that is too large bash, too tall to gouge but is susceptible to fireballs..
-Finally, make some zones too hard to clear without teamwork.
