I have just read First, Break all the Rules by Marcus Buckingham. I highly recommend it. There are many pearls in the book:
Here is a sure way to lose your best people:
Spend all your time helping the strugglers.
If you want to excel, invest in your best. Learn from your best, discuss things with them, understand what they do that makes them excel. Don’t spend all of your time investigating failures, study what is working really well. Challenge your best, leave the average, acceptable level of performance, push a little every day.
This doesn’t mean ignoring the weaknesses, handle those, but give you biggest focus to your best people.
Who are your best developers? What do they do that others don’t? How do they excel? Spend time with them.