This paper poses a question of direct relevance for welfare administrators, program operators, and policy makers: What management practices, program strategies, and local conditions are key to running effective welfare-to-work programs? To address this question, the present analysis links detailed measures of program characteristics to valid and precise estimates of program effects on short-term earnings. Data for the analysis are drawn from these three random assignment studies of welfare-to-work programs in 59 sites across the United States (with a combined total of 69,399 welfare clients): California's Greater Avenues for Independence (GAIN) program, Florida's Project Independence (PI), and the National Evaluation of Welfare-to-Work Strategies (NEWWS). The findings indicate that, other things being equal, program effects on earnings during the first two years after random assignment are largest when programs strongly emphasize employment, provide personalized attention, and do not let staff caseloads become large. The paper also finds that short-term impacts on earnings are smaller where unemployment is high, management choices and practices matter a lot, increased reliance on basic education reduces short-run effects, economic environment plays an important role, and program effectiveness varies inconsistently with client characteristics. Appendixes include 54 references; data tables and figures; program models for GAIN, PI, and NEWWS; and descriptions of measuring program performance as program effects on client earnings, measuring program characteristics, and testing the sensitivity of findings from the impact model. (Contains 54 references.) (Author/YLB)