What are the tell-tale signs

a young manager will make it big? or is it impossible to predict for us fans?

Look at Conte for example, making it happen with Juventus, or the rise of AVB?

raping Barcelona with a very inferior squad helps

ergo Pochettino

i think it largely depends what team your based in say for example like doc mentioned sir alex went 5 years without winning a trophy yet they still stood by him until he did and thats when he learnt the trick look at him now his team doesnt even need to play good to win games

another example(albeit the total opposite is Del Bosque who won things straight away.... i mean its impossible to predict, sometimes Managers really need time and support to grow and put that confidence into his players and sometimes they only need a comfy bed and a house and the trophy would be by your doorstep next thing you know

I guess one question i should have added is, How important is the role of management in the coach selection?

I think with Conte and Juve its obvious though, hes really changed somethign about them, and its hard to see it going backwards so im pretty sure they will be pretty successful or at least very much improved now.