When the Selection Criteria becomes very complex for any given report, I often find it helpful to display the whole Selection Criteria right on the report.
To do this, you need to insert a "Special Field" from the Field Explorer.
1. Select Insert | Special Field.
2. Drop down the Special Fields list.
3. The field we want to insert is Record Selection Formula.
4. You will also notice that the Group Selection Formula is also available here.