Mentoring for principals during their first years on the job, once a relative rarity, is now required by half the nation's states--a major advance from a long-standing "sink-or-swim" attitude toward new school leaders and a belated sign of recognition of the role that well-prepared principals can play in lifting student achievement. But an analysis of this new trend by the Wallace Foundation concludes that too often, many such programs are not yet tailored to develop principals capable of driving better teaching and learning in their schools--and shaking up the status quo when necessary. This publication features close-up looks at mentoring programs in two school districts--Jefferson County Public Schools, and New York City through its NYC Leadership Academy--that have put particular emphasis on getting mentoring right, with varying degrees of success to date. Based on its analysis, the report proposes several "quality guidelines" that might be broadly useful to states and districts either thinking about adopting new programs or improving existing ones. (Contains 35 endnotes.) [This document was published by the Wallace Foundation.]