Getting grouping right in Report Builder
One thing Report Builder users need to be aware of when building a report is the difference between an entity group, which displays exactly one instance for each row in the underlying table, and a value group, which displays one instance for each distinct value of a particular field. The type of group they get depends on the field(s) they used to create the group initially. Problems can arise if the user intends to create an entity group with many fields, but instead creates a series of value groups (one for each field). This may make it impossible to get the sorting they want, and can introduce unwanted subtotals levels as well.
For example, a user might drag in the Last Name field as the first step in creating an Employee report. However, if the DiscourageGrouping property for this field in the report model is "false", dragging in this field creates a value group on Last Name. This means that the group cannot be used to display data about individual employees; it can only show totals for all employees with a given last name. So, other fields that are not totals (e.g. First Name) must be added to a new group. If they also do not discourage grouping, a value group will be created for them as well. And so on...
The safest way for the user to get an entity group when they really want one is to drag in the entity itself from the entity list, instead of dragging in a field first. This will create an entity group displaying the DefaultDetailAttributes or IdentifyingAttributes for that entity. This is also a convenient shortcut for adding the fields they almost certainly want to include anyway. As the developer of the report model, you can help users who are unaware of this trick by setting the DiscourageGrouping property in the report model on any field for which users are unlikely to want a value group. They can still get one in their report by using a custom field that simply references it, but the default behavior will give them an entity group instead.