It's best to start by gaining a solid understanding of your prospective users, what their goals are, and how they go about their work. For broadly-targeted groupware applications, such as videophones or email, understanding users can boil down to understanding how human beings communicate in the first place. A design is also best informed by conducting user studies on system prototypes. Group interaction style is hard to select for beforehand, whereas individual characteristics are often possible to determine before a study is conducted. Pre-established groups vary in interaction style, and the length of time they've been a group affects their communication patterns.
New groups change quickly during the group formation process.
Many studies need to be long-term, especially when studying asynchronous groupware. Modifying prototypes can be technically difficult because of the added complexity of groupware over single-user software. In software for large organizations, testing new prototypes can be difficult or impossible because of the disruption caused by introducing new versions into an organization. When designing groupware, it is often best to begin with field studies. The goal is to understand a particular type of group or organization that will be using the groupware system.