I may end up regretting this as I fall down into a black hole of reading the NHL rule book, but I thought it might be helpful to have a place where people can ask about various rules and how they work.
I am by no means claiming to know all the rules or an ability to explain them clearly. I know a few of the ones that have come up lately, though, and figured I could at least get the ball rolling. I also have a link to the NHL rule book online (Here) and am somewhat familiar with how to read it to find answers to rule questions.
I'll try to answer or look up what I can if there's specific questions (and I bet there's more than a couple other people who can answer some questions I won't be able to) and provide practical examples where I can.
The first three I came up with are on the other side of the jump...
The team may call up players as many players they want as often as they like before the trade deadline, so long as they remain under the cap. After the trade deadline, the team is limited to four call ups except in case of emergency. An emergency is only declared if the team will have fewer than 2 goalies, 6 defensemen, or 12 forwards (in other words, less than a full playing roster) at the time of a game. The team may not call up a player who does not have an NHL contract with them, regardless of that player’s association with an affiliated AHL team.
Practical example: The Sharks can run the Worcester Shuttle on a daily basis with as many players as they wish until the trade deadline. After the deadline, they must choose wisely and only call up players as needed; Mashinter replacing a suspended Heatley, Desjardins replacing an injured Nichol, etc. If half the team suddenly became sick, they could call up half the Worcester Sharks until the emergency passed without affecting the call up number after the deadline. They cannot call up Cheechoo because he has not signed a contract with the NHL Sharks, only the AHL Sharks.
Visors while fighting
This rule is multifaceted (read: confusing as heck). You are not allowed to START a fight while wearing a visor without attempting to remove it, if the other player does not also wear a visor. You are, however, allowed to keep your visor if the OTHER PLAYER starts the fight or if you both wear visors (though both are considered bad form). Referees are given the discretion to waive this penalty if a player is attempting to remove the visor but cannot get free long enough to do so. Note that many players who fight frequently forgo visors to avoid this rule (Clowe and Parros, for example). A big part of this rule is to prevent injuries caused by punching and potentially shattering a visor.
Practical example: Douglas Murray is attacked by two players. Dougie wears a visor, but because he’s being attacked, he doesn’t have to shuck his visor and probably doesn’t have time to do so anyways. Dan Boyle comes in and takes on one of the guys after Murray. Boyle also wears a visor and doesn’t remove it. He takes the penalty because he didn’t try to ditch the visor and "started" the fight between him and the person he is fighting.
First and foremost, a goaltender may not take a faceoff (okay, I know everyone knew or could guess that). The linesman is expected to wait for all substitutions to occur, then blow his whistle to inform the teams that they have 5 seconds to line up for the faceoff (though jostling by the wingers/defenders and re-positioning by the centers can often make this take longer).
If one of the centers refuses to line up, he may be tossed by the linesman. If one or both centers refuse to put his/their stick down to the ice in the ready position, they may be tossed. If a player other than the centers encroaches on the circle, the center may be tossed. If the center or any other player makes physical contact, the center may be tossed. If a player lines up on the opposing team’s side of the ice, the center may be tossed.
If these things go on long enough (officially, two violations is enough), the team may be assessed a delay of game penalty, though it almost never happens. The linesman may also drop the puck if one player is ready and the other is not after 5 seconds. Similarly, if a player is tossed and his replacement is too slow to get into position, the linesman is allowed to drop the puck.
Practical example: Scott Nichol is about to take a faceoff. His teammates line up behind him, facing toward the opposing team’s goal and are careful not to cross over into the opposing team’s side of the faceoff circle. The linesman blows his whistle and Nichol skates quickly to the dot and gets into his stance. He leans forward, close to the dot and puts his stick close to the ice. His opponent, however, is trying to hold back and doesn’t come to get ready for about 5 seconds. The linesman tosses that player and his replacement comes in. The replacement isn’t as prepared for Nichol’s positioning and touches Scotty. He’s violated the faceoff rules and is also tossed. The linesman can assess a delay of game penalty, call for another player to replace the offender, or drop the puck while Nichol is the only one who can play it.