What are the common "non-blunder" mistakes non-beginners make?

I would think so. Not that he would necessarily want to play h6 g5 or take back with gxf6, but it would become an option I guess.

In some french lines black doesn't mind playing Nh6 for example, allowing the ugliest of kingside pawn structures with Bxh6 for the sake of an open g file.

I'm not so sure, because I don't think ...h6 and ...g5 is even bad when you're castled (of course this only applies when ...Nxe4 winning the pawn can be played!).

The position in your diagram, despite the fact that black can force Bxf6 with ...h6, that position is perfectly fine for white, though the pawn center can end up rather immobile whilte black eventually opens the center and activates his bishops. How well do you remember what the book said? You may be taking it out of context because pins are made all the time before the opponent castles, because usually ...h6 and ...g5 if it doesn't win material even if black isn't castled usually is too weakening because a lot of times queenside castling isn't a good or quick option for black but now he can't rely on the kingside either.

There are some nimzo indian lines though where black plays ...g5 because the pin is so annoying and considers queenside castling, but it's by no means bad for white.

I wouldn't want my pawns doubled in that position (the current diagram, not the french one). It's a little weakening and inflexible, and castling queenside (and as black it's always riskier) against a two pawn center seems dangerous, all for the g file.

I was surprised too, but theory says black is fine in some situations. I'll try to find an example.

I'm talking about the diagrammed position. In the french that does happen sometimes, though not in the lines I play.

Most of these suggestions seem like they could be summarized by

1. Not recognizing the imbalances and not doing everything to strengthen the imbalances that favor your and limit the ones that favor your opponent.

2. Playing without a plan. 

Good discussion though

I don't remember it well at all, and very probably I am taking it out of context.  I just recall that when I read it, it seemed as if the advice was offered as a general tidbit, not just specifically to the situation being discussed.  It may not have been a book-- could have been some nobody just making a comment in forum somewhere, but it stuck with me, and I've wondered about it occasionally.

Oh OK, I wasn't reading properly, sorry. I was talking generally in my earlier posts too. Anyway, for completeness' sake :

Hey, I attended a 5-day chess camp where Greg Kaidanov was our main lecturer each day!  He's a nice guy.

And the Anand-Kramnik games I mentioned, not Bg5 related but at least gxf6 related with no castling :

Good night enjoyable thread.

Underestimating your opponent. I once played a 12 year-old, little did I know he was the best 12 year-old in Canada >_> He was an Albertan kid, he was 2164. I played very lax.

very good point, chessowns - my first county game in England I was paired with a small boy and he was rated some 500 lower than me FIDE - I was about 2000 at the time. Well I was a little disappointed to say the least cos I figured I'd rather have spent the day doing summink else (with travelling and the match, the wholeday was a right-off). Anyways, I didn't really give it my full concentration - I was wondering what I was gonna do with the rest of my day in a strange town where I ddn know anyone cos I ddn expect the game to last too long. - I was right about that! - I made an idiotic blunder on move 8 - game over in no time So I apologised to me team captain and went out for a drink with the lad's father then we came back an' I played the lad a few more times an' gave him some lessons an' his father some advice on how to coach him - so the day ddn work out too bad in the end - cos I learnt a valuable lesson too ( this incident occurred about 2 weeks after I had just won a tourney in Wales and beaten an IM in a money match ! )

hmm greatest mistake for beginners..challenging me! muahahaha!

but seriously, you guys are all dead right. nothing screams beginner like bringing the queen out on move 2.

Well I think the most common mistake for non beginners is using your trump card right away. If there's no urgency, than holding a small weakness hostage can lead to a bigger advantage rather than cashing it in right away.

Also, play to your rhythm.

I don't know if this is too beginner, but overvaluing checks you can give / overvaluing the checks your opponent can give; and I don't just mean checking to check, but when calculating a line where you're going to let your king cover get blown open but the checks run out after only two after which you're perfectly safe, it's worth realizing you're still safe...

Same for when you get to open up their king and start checking, but if they win a rook and your checks run out it doesn't mean much.  I was playing some blitz yesterday and ran into some opponents like this so that's why it's on my mind, may or may not be a good one to add.

It wasn't Eric Hansen was it?

Hey, I also attended the Kaidanov Chess Camp. Totally agreed, very nice guy.

I'm jealous of you guys, where can I get a schedule of these Kaidanov lectures?  Does he tour around or is it all on one area?  I guess I could simply google it but... I'm lazy lol.

The camp I was at was the annual summer chess camp at St. Olaf College in Northfield, Minnesota (25 or 30 miles south of Minneapolis).  It's put together each year by Kevin Bachler, but Kaidanov has been an instructor there every year for quite a few straight years.  This year it runs from July 25-30, and the scheduled instructors are Gregory Kaidanov (GM), Yury Shulman (GM), and Irina Krush (GM).

I attended in 2005.  The camp is set up for kids to be able to attend, and attendee ages ran from around 10 (some kid named Daniel, who beat the GM in the opening simul and no one was surprised-- the instructors had already heard of him) to middle-aged adults.  There are 3 different levels of lectures that run concurrently from near beginner to the one Kaidanov ran, which was the most advanced (and much of that was above my level to fully appreciate, but I'm still glad I opted for the advanced level).  There were a fair number of adults who attended, including some pretty good people who regularly played tournaments, and several of the adults attended with their own kids.  I just attended by myself for my vacation and stayed in a nearby motel.

Kaidanov is there every year.  He said it's one of his favorite regular chess get togethers.  I don't know if he always runs the most advanced section, or if different instructors rotate among the different levels each year.

They have housing and meals on campus, or one can opt to lodge elsewhere but still take the meals on campus.  By the way, St. Olaf's is a really neat campus-- nice hills, trees, and cool architecture.

--Cystem

Thanks for the description (and link), sounds like a great experience.

Many thanks to all who have contributed. Updated the original post some more to the best of my filtering-for-content ability.  Turned out to be a really helpful discussion ... chess.com rules :)