Not completely sure this should go here, but I have a question about deck problems:
“If the deck is discovered to be incorrect during the presentation period, and the missing cards are not in the opponent’s deck, the penalty is a Game Loss.”
My question is - as the opponent is presented with a deck, what is s/he allowed to do in order to check if it's correct or not?
According to MTR 2.3 - “Players present their decks to their opponents for additional shuffling”, and that's it. I'm not even sure the opponent may count the cards, as one could argue that might take too long and exceed the given pregame time (though personally I would allow it).
Are there any “healthy habits” we can educate the players to do at this point?

For the opponent, there is not that much he can do to notice deck problems at this stage. This is one more reason why we do deck checks at competitive REL and higher ;-)


There is the sideboard presentation part of the pregame procedure (MTR 2.3) where there is a chance an opponent could see something is wrong (ex.: 16 cards sideboard being presented). But that part of the procedure is not common practice everywhere. So consider it a corner case.

Or you notice a potentially marked card during presentation, but that's a different infraction.


We expect each player to present a legal deck each game so any tips and tricks we can really give are more related toward their own deck than their opponent's.

Examples:
1. Take the habit and time of de-sideboarding after each match.
2. Count your sideboard before shuffling and present.
3. Players are allowed one “pile shuffle” of their own deck per game for counting purposes.
4. If you discover a deck problem with your deck, call a judge on yourself immediatly.

Players can, do, and maybe should count their opponent's deck when presented; the new limit on pile counts doesn't prevent that. In fact, the philosophy of the relaxed penalties re: deck problems stands firmly on this foundational idea, that you have this one opportunity to verify the deck; if you abdicate that responsibility, you're accepting the legality of the deck.

d:^D

I know several players who do a “2-pile count” during the presentation period, particularly after that big stink with the guy palming his opener.

This also gives a window for a player to point out exiled cards that didn't get returned. If a player has the classic Oblivion Ring off to the side they forgot to shuffle back in, their opponent isn't obliged to tell them. They can wait until they present, and then use this window.

This might not be a particularly sporting or nice play, but this window does exist.