Now I don't get to attend or watch every home game, but I can't remember the last time that a defenseman, or for that matter a non-scorer who played well, was one of the three stars at a Ranger home game. Who picks these guys? Guaranteed, it's always Lundqvist, the game winning goal scorer and Jagr if he has scored a point or two. I've watched some of our defensive players (Girardi, Tyutin, Staal, Betts) play splendid games and not get recognized. Sometimes I feel like I could do a lot better sitting at home than whomever does this at the rink.
It's selected by the "professional hockey writer's association" which just means whatever beat writers are on hand for the game. From what I've seen (not at the Garden) is that they just throw out names until a consensus is reached.
I've been asked to pick 3 stars at a few college hockey games (as a writer for our campus radio stations website), the PR director asks all the media members who their 3 stars are, and you just give him 3 names.
At that level, its a very informal process.
I think Weinman wrote about it last year, he gets a sheet of paper in the start of the 3rd, and at the last media timeout, he has to give it back with the 3 names; he gives it very little thought.