Prompt is a great word to think of here as is advise, positive, concise, confident and authoritive.
The skill of being a good team player is getting someone to do what you want them to do and make them believe it was their decison.
Somebody quoted the Staines disaster above but Tenerife is much more relevant. The FO should have stopped the captain from taking off-the irony is that the worlds worst air disaster could have been prevented by a quality that many indivduals have and needs no special training.