Should I speak to the officials before or during a game, and how should I give feedback?

The supervisor's handbook says it depends on the game, the officials and the reason for supervising:

• Experienced officials: if seeing them in the referees' room before the game will not upset them, it may be fine to do so.
• Inexperienced officials: if knowing they are being supervised could influence them, it may be better not to see them until after the game.
• Assessing after adverse reports: stay inconspicuous and observe without the official knowing they are being assessed. After the game it is permissible to discuss their work in that game.

Communication tips from the handbook:

1. Be honest: do not tell officials one thing and report another.
2. Be objective, and if you report something critical, offer a method or solution.
3. Listen, so there is no misunderstanding of your comments.
4. Be sympathetic with inexperienced officials.
5. It is usually acceptable for linespersons to listen in when you talk to the referee, but for a very critical discussion you may want to talk only with the referee.
6. Talk to both linespersons in the presence of the referee, to encourage teamwork. In the two-official system, talk to both officials at the same time.
7. Never be openly critical of game officials or the association you represent.
8. Keep your report and comments private: the report is confidential.
9. Be beyond reproach in your actions and comments.

Never influence an official's decision, or cause them to change it, during or after a game. The final decision on all game matters rests with the officials on the ice.

Source: Hockey Canada supervisor's handbook (Canadian Hockey Association, revised June 2001), Communicating with Officials and Qualities of an Effective Supervisor.