Gimme Five

• WWizards of the Coast2018-01-19
  Official Ruling
  A silver-bordered game is one where at least one silver-bordered card was in one of the decks. The silver-bordered cards in a silver-bordered game don't necessarily need to be visible for the players to gain 1 life for high-fiving you.
• WWizards of the Coast2018-01-19
  Official Ruling
  You must offer high-fives to other people and they must voluntarily accept for it to count.
• WWizards of the Coast2018-01-19
  Official Ruling
  Each person who high-fives you counts only once, no matter how many times they high-five you.
• WWizards of the Coast2018-01-19
  Official Ruling
  The person timing you should let you (and other players in your game) know when 30 seconds has elapsed. You don't have to be back in your seat at the end of the 30 seconds.

Rulings via Scryfall