I won't remind them the first time, but most of the time when I hit my button (which doesn't need to be pressed) and it makes a different sound, my opponent will know of his mistake. If he doesn't, I'll probably tell him. It's automatic for me in OTB games to make my move, then slap the button, regardless of whether it needs to be pressed.
A question about sportsmanship in chess

I think it depends on the player and the situation. If it is someone who made the mistake once, I'll go and make my move and hit the clock gesturing politely that it wasn't done in the first place. After that, chess is chess. I also know of certain players that will cheat at anything you give them a chance to. I'll wait for the last second to tick by for them.
Come on. Burdened with managing your opponent's time??? What a bunch of hot-air rhetoric for "I'm an a##hole who will take a win anyway I can." You guys sound like blowhard politicians. It is in no way a burden to gesture to your opponent unless you are quadriplegic.
Now that you have everyone's attention, are you really such an idiot?

banjoman> I forgot to hit the clock after a move, and 10 minutes or so elapsed while my opponent happily pondered his move on my time.
When I played a student of mine two weeks ago, she forgot to press the clock. I let it stand and spent the next twelve minutes considering my next move. I would've won anyway, but it was a lesson she needed to learn.
banjoman> Would you be happy to win a game because...
Games where my opponent blunders are generally not the most satisfying, but there's some satisfaction in efficiently punishing their mistakes.
The clock is an integral part of the game.
in a friendly game.. give reminder. else, no. cause u may actually break someone else concentration, which is also unsporting. I think.
Thank you for supporting my point that those who are for ignoring an opponent's time blunder are blowhard a##holes. Couldn't have done it better myself. And what does everyone having my attention have to do with your childish question? Am I supposed to say, "Well, before everyone had my attention I was not an idiot, but now that they have it, I am." Or perhaps you are merely calling me out in front of everyone. I can't tell because your writing is unclear.
Here's one for you: now that you have my attention, do you possess the reasoning skills of a primate?

". . .my point that those who are for ignoring an opponent's time blunder are blowhard a##holes."
Thanks for shining the defining light of rational argument into such a dark topic.
"do you possess the reasoning skills of a primate?"
Just for the record . . . humans are also primates.

well life isn't fair, life is hard, people won't always hold your hand and wipe your nose for you.....the only place success comes before work is in the dictionary, there is no free lunch (although alot of parasites in the USA think there is) hopefully you learned something from that incident and won't become a little whining crybaby..............t/y for bringing up the incident so i could get some feelings out...........

ohhhhhhhhh, batgirl that quote on your post # 42 was good, im gonna be borrowing that alot for conversations, t/y
there are more important things in life than worry about a silly chess clock. if the game is friendly, I think one should remind his opponent, but if it's a formal game, a tourney etc, then one should keep quiet and mind his/her own game! Like in any other games,chess has it's own refs.

To sum up, it appears that a majority of the commentators prefer to exploit an opponent's clocking mistake. Others agree with me that, besides costing you nothing, it is better to gesture at the clock at least once.
A lot of people justify their position by saying "thems the rules." But there is no specific rule against reminding your opponent to clock. I found this quote on wikipedia, which is sourced to Schiller's "Rules of Chess" (2003): Generally a player should not speak during the game, except to offer a draw, resign, or to call attention to an irregularity."
Gesturing at the clock is, on the face of it, an acceptable instance of calling attention to an irregularity. So the rules really have nothing decisive to say about this whole issue. The question is about how to conduct yourself in competitive chess. Instead of trying to hide behind the rules (unpersuasively), those who choose not to gesture at the clock should just admit that they are making a deliberate choice to exploit their opponent's situation.
I don't think that's an "evil" choice. I just don't see why anyone would prefer to gain an advantage that has nothing to do with chess skill. I think it's a case of putting the desire to win above a sense of fair play.
Granted, if the opponent's clock problems are habitual and a nuisance to you, it is stupid to waste your time on them. I am talking about instances where it would cost you nothing, not even a moment's thought, to make a quick gesture with your hand so that the game can continue as normal. I think that is a sensible policy.

Its strictly a personal decision. In games where clocks are involved handling the clock and remembering it is part of the game. The rules do not forbid you from reminding him about the clock but the rules also do not require it. Over the years I have sometimes reminded my opponent but in the majority of cases I do not.

No, I wouldn't tell him (not in a tournament). Nor do I think many professionals would.
This actually happened once in a world championship match, by the way. In one of the K vs K duels, Kasparov did forget to punch his clock after a move. I don't recall the details...I think after several minutes he realized his error, and no doubt gave himself an internal smack on the head for it...but I can't imagine any onlooker expecting Karpov to point out his gaffe to him. Clock management is as much a part of the game (in competitive chess anyway) as finding good moves; and commentators talked about Kasparov's omission in the same way that they would discuss a major blunder over the board.
Did Kasparov ask Karpov why he didnt remind him of his clock?!
Managing time (in the sense of making good decisions about how to spend it) is a chess skill in an interesting sense. Remembering to punch the clock is a chess skill in an uninteresting sense. I would take some satisfaction in winning a game because I made better decisions about time management. I would take no satisfaction in winning because my opponent forgot to punch the clock. In formal and high-level play, I understand the need for rules and customs that don't permit one player to point such things out to the other. And I can't say that I think anyone is "obliged" to point it out in play of any sort. But personally I would point it out (if I was in a setting where it wouldn't be considered inappropriate, and it wasn't a chronic issue), just because I'd rather make the game a contest of interesting skills than a contest of uninteresting ones. (I wouldn't want to get an advantage from a clerical error made by my opponent in recording the moves, either, because that too is an uninteresting skill.)
I would tell anybody if there was absolutely nothing on the line. If it was in the tourney, I would let it run out for all games that matter, but I may remind someone I know in a less serious game after a portion of time had elapsed.