The book-length resource I’d point to in answer to the first question is Brian Croft’s Test, Train, Affirm, and Send Into Ministry: Recovering the Local Church’s Responsibility in the External Call.
The best book I know of for potential or prospective pastors and leaders is Dave Harvey’s forthcoming Am I Called? The Summons to Pastoral Ministry, with a foreword by Matt Chandler.
And here’s a new 10-minute TGC video with David Helm, Mike Bullmore, and Bryan Chapell talking about how to identify such leaders:
For more of Harvey’s perspective, see the following discussion: