Pick recruits with high IQ, demonstrated ability, and a good moral compass.

From The Validity and Utility of Selection Methods in Personnel Psychology: Practical and Theoretical Implications of 85 Years of Research Findings by Frank L. Schmidt and John E. Hunter. From the Abstract:

This article summarizes the practical and theoretical implications of 85 years of research in personnel selection. On the basis of meta-analytic findings, this article presents the validity of 19 selection procedures for predicting job performance and training performance and the validity of paired combinations of general mental ability (GMA) and the 18 other selection procedures. Overall, the 3 combinations with the highest multivariate validity and utility for job performance were GMA plus a work sample test (mean validity of .63), GMA plus an integrity test (mean validity of .65), and GMA plus a structured interview (mean validity of .63). A further advantage of the latter 2 combinations is that they can be used for both entry level selection and selection of experienced employees. The practical utility implications of these summary findings are substantial. The implications of these research findings for the development of theories of job performance are discussed.

IQ is the most predictive measure to forecast performance. It is also the cheapest to administer. It is also, generally, illegal.

Work sample tests are used for the purpose of judging a person's ability to do an assigned job and evaluating them based on their performance in the particular job.

Integrity tests are a specific type of personality test designed to assess an applicant's tendency to be honest, trustworthy, and dependable. A lack of integrity is associated with such counterproductive behaviors as theft, violence, sabotage, disciplinary problems, and absenteeism.

So the best method of recruiting is to pick recruits with high IQ, demonstrated ability, and a good moral compass.

You wouldn't think that could be controversial but there are lots of State efforts to avoid that simple approach.