One of the basics which merits a visit every so often is the role of the cover officer — something that very likely had an influence over the "go/no-go decision" for violators in some of the videos we see all too often of officers being assaulted by violent subjects.
Every so often, a team's discipline on their division of labor in the contact/cover tactics will erode, with the cover officer collapsing in and engaging the subject (or subjects). This does a variety of things, from creating the potential for conflicting commands and questions to be thrown at the individual to opening up possible routes of escape from and/or assault on the contact officer.
The terrain will, to a certain extent, determine your tactics — your exact positioning relative to he subjects, will be affected for example by the need to have visibility around the corner of a building against which the subjects are sitting, for example — but some general rules of thumb always apply.