This report identifies the concrete practices that set exemplary principals apart from their peers, exploring how they assemble the strongest-possible staff and foster a culture where teachers--and their students--are supported to success. The researchers conducted an in-depth analysis of data sets from two studies conducted by New Leaders from 2007 to 2011: the Urban Excellence Framework™ (UEF) case studies and the Effective Practice Incentive Community (EPIC) case studies. Both data sets were chosen because they identify and analyze principals whose schools made better-than-average gains in student achievement. These principals across both studies are referred to as "highly-effective principals." The Urban Excellence Framework data set consisted of case studies made during site visits to New Leader schools. The EPIC data set consisted of case studies of New Leader and non-New Leader schools that had relatively higher value-added scores than other schools in their district or charter consortium. For both studies, researchers conducted site visits and interviews, then coded the information they collected according to New Leaders' Urban Excellence Framework, which outlines the leadership and school practices that drive dramatic gains in student achievement. This Framework includes the entire range of leadership practices, but for the purposes of this study, researchers focused only on those actions that related to teacher effectiveness. In order to form a clearer picture of the specific ways these highly-effective principals influence teaching, the researchers re-examined the case study examples that had been coded as related to teacher effectiveness according to the UEF framework. Great principals amplified great teaching by working in three intersecting areas: (1) developing teachers; (2) managing talent; and (3) creating a great place to work. This report discusses the numerous and specific ways the principals in the study pursued each of these goals, including the ways in which some actions served multiple purposes at once. A bibliography is included. [For the executive summary, see ED585109. For the policy brief, see ED585110.]