At a new store, where I was playing and not judging, there were a few guys there who, while between rounds, they admitted to knowing that their opponent missed several triggers (i.e. not putting counters on, not gaining life, etc). I told them that they knowingly let their opponents missed it and therefore were cheating.

Additionally, there were another few people who were watching and allowed it to happen.

I am sure you guys have already dealt with these issues in the past, but what has worked the best for you guys?

Under the current revision of the JAR you are not required to point out your opponents missed triggers. They were not cheating.

Even when it has an impact on the game state?

Yep, it's true. You do not have to point out your opponent's missed triggers, though you may do so. Here's the section from the Judging at Regular REL document that applies:

A player forgets a triggered ability (one that uses the words “when,” “whenever,” or “at the beginning”
usually at the start of the ability's text).

These abilities are considered missed if the player did not acknowledge them in any way at the point that it required choices or had a visible in-game effect. If the ability includes the word “may,” assume the player chose not to perform it. Otherwise, add it to the stack now unless it happened so long ago that you think it would be very disruptive to the game - don’t add the ability to the stack if significant decisions having been made based on the effect not happening! Unlike other game rule errors (which must be pointed out), players are never required to point out their opponent’s missed triggered abilities, although they may do so.

Note this policy only applies to triggered abilities. For instance, you can't let your opponent forget to gain life from lifelink, because that's not a triggered ability.

Edited Nathan Long (Jan. 26, 2014 11:25:06 PM)

Well, gaining life was one of the things they were letting slide - also a few spectators allowed a player to cast something without the proper mana (both of the players did not notice it).

The main problem I am trying to combat is that the people who noticed and didn't say anything were the more experienced people and those who were committing the errors were newer. I'd like to foster a learning environment and not a pseudo-Comp REL environment at FNM.

Teach the difference between missing triggers and things like casting a
spell with wrong mana. One of those is bad. If you are not the judge
running the event, lead by example… be the spectator who interjects and
says something. Get the judge involved.

When I overheard this, I talked to them. And a lot of them were getting pissy with me when I would interject on something like improper lifegain, not the right amount of damage taken, that sort of thing. And this is one of the stores that I will judge their bigger events, so I don't want to alienate them from the get-go, but at the same time I don't want them to do the wrong thing.

spectators are not required to point out anything they see that has gone
wrong with the game.

Sam, spectators are absolutely not obligated to point out issues. We do
strongly encourage it, however. What the MTR has to say about spectators:
1.11 Spectators
Any person physically present at a tournament and not in any other category
above is a spectator. Spectators are
responsible for remaining silent and passive during matches and other
official tournament sections in which
players are also required to be silent. *If spectators believe they have
observed a rules or policy violation, they are *
*encouraged to alert a judge as soon as possible.* At Regular or
Competitive REL, spectators are permitted to ask
the players to pause the match while they alert a judge. At Professional
REL, spectators must not interfere with
the match directly.
Players may request that a spectator not observe their matches. Such
requests must be made through a judge.
Tournament officials may also instruct a spectator not observe a match or
matches.

Emphasis mine. We don't penalize them for not pointing out things, but
telling people “it is a good thing for you to point out issues in matches
to judges” generates positive effects at every level of play.


~Rob McKenzie
Magic Judge Level III
Minnesota

Originally posted by Rob McKenzie:

We don't penalize them for not pointing out things, but
telling people “it is a good thing for you to point out issues in matches
to judges” generates positive effects at every level of play.

I think I will use this verbage. As it is what I want to foster at my store(s), a fun environment that also helps people learn and grow as players.

Originally posted by Darren Horve:

And this is one of the stores that I will judge their bigger events, so I don't want to alienate them from the get-go, but at the same time I don't want them to do the wrong thing.

Even though it is possible that your behaviour might seem abnormal to them (change is hard) and you take some risk of alienating some, the fact that you'll be their judge for bigger events is one of the best reasons to set the example you want to see from them when you are playing. Imagine how much harder it will be if you do not set the example and then it comes up when you are judging that they observed you not doing what you wish for them to do.

Also, remind your players that at REG, the key is fun and fairness and having the game be played more than the tricks of rules lawyering. That's why we have judges to step in when anyone is not sure of something and you're there to help. One thing I often say to my players at REG is that for FNM and other such events, our main goal is to have thing go right and to fix things whenever we can. As such, I hope that my players will help me achieve this goal so that everyone - honoured elders and new players alike - will feel like my shop is a place where they can play safely and without fear of sharks.

It is also worth trying positive enforcement. Make a point of obviously thanking spectators who do call issues to your attention rather than just chiding those who don't, for example. It demonstrates clearly the kind of behaviour you want.

Having reread the thread, some bullet points for clarity:

-Spectators are never required to point out or get a judge involved for infractions that they observe in another match. You probably want to encourage them to call you, however.
-Players are never required to point out their opponent's missed triggered abilities. At Regular REL, depending on how competitive your group is, you may want to encourage them to do this.
-Players are not allowed to intentionally miss their own triggers. Players are required to point out or call a judge for any other infraction that they notice in their match. Failure to comply with knowledge and intent is a Serious Problem for which the player should be disqualified from the event.

Note that calling a judge is far better than just pointing it out ;)