Not a rule, but a mechanic - Calling Penalties

The most visible part of an official’s role is the assessment of penalties. When an infraction occurs and play is stopped, everyone involved with the game has a tendency to focus their attention on the officials. For this reason, the way an official behaves while assessing penalties will determine
much of the respect and credibility the official will receive.

Procedure for Calling Penalties

• During Play, the official will give the delayed signal to signify an infraction
• The official will stop play with the possession of the puck by the offending team
• The official will come to a complete stop
• The official will assess the penalty by pointing in the direction of the player and verbalizing the number of the player and the color of the team
• The official then signals and verbalizes the infraction
  • Good Signals are a form of communication!! 

Rule 304 - Protective Equipment

Is it legal for a player to skate with their jersey tucked into their pants?

Yes. Rule References 304(h) and 203(b).

Although Rule 304(h) states that all protective equipment must be worn in the manner in which it is intended, the jersey is not considered protective equipment. In youth hockey, it may be difficult for a team to have proper sizes for all of the players and as long as the identifying number is visible, the official should not make this a bigger deal than it needs to be.

 Rule 639 - Tripping

For a tripping penalty to be assessed, must the fouled player fall to the ice?

No. Rule Reference 639(Note).

The Rule uses the words “trip or fall” to describe the offense. In the case where a player does not fall, it must be clearly obvious their progress was impeded and a competitive advantage was gained as a result of the tripping action.