I don't understand how it's possible to have an opening repertoire...

People always say, "I always play such-and-such opening," or, "My favorite opening is such-and-such," but how can they possibly say that? There are basically two possibilities: if you play as black you have to defend against any possible opening from white, and if you play as white you need to be prepared for any possible defense from black. If we assume there are, say, 10,000 combinations of openings/defenses, the chance that you will ever play the same opening twice in your entire lifetime is pretty slim...

So, I don't understand how people can learn the theory in any useful manner. Unless you are a grandmaster who actually does know all 10,000 opening scenarios, what good is it going to do you to know one or two, or even a dozen? Even if you learn the popular openings and are prepared for half of the games that come your way, what do you do for the other half that use esoteric openings? Give up and resign?

In my own personal experience, I don't think the first five moves of any game I've ever played in my entire life have been the same. Even if I deeply study an opening up to move 10, 15, or 20, the chance that that move sequence will ever come up in a game that I actually play is basically zero. I mean, this is what keeps chess from being boring, right? The fact that every game is different.

So, I'm leaning towards opening principles being more important than specific opening lines themselves, but even so, a lot of lines arise because in-depth analysis reveals that if you make the wrong move then a certain combination of five other moves will do this, that, and the other thing and leave you in a bad position, which you would never notice if you hadn't studied it.

Also, I find it kind of annoying that most opening explanations tell you why the good moves are good, but nothing about why the other moves would be bad. In real games, your opponent often doesn't play the best move, but it's very difficult to exploit any sort of mistake on his part because there's nothing "obviously wrong" about the move he just played even if you know the theory, because the theory doesn't deal with that move (or because that move simply transitions into a different opening).

Anyway, that's my rant for the day :-)

I wouldn't exactly consider this a rant. And if you've never played the same first 5 moves twice, then you obviously haven't played very much chess. Sorry.

Even average players can have an opening repertoire. This doesn't mean that it is exhaustive and prepares for every eventuality in the opening.

For example, I picked up the Modern (e4/d4/c4... g6) to handle much of what I can expect from white on the first move. As white one can play Nf3 and go for KIA or Reti. I sometimes employ Larsen's Opening 1. b3 and don't have to study reams of theory for it.

If a player is more ambitious he can prepare himself for openings like Ruy, Sicilian, Caro, French, QG, English, etc. and just be ready as best he can. It does sound like a lot of work, but opening knowledge is something you just continually add to, even if much of what you know becomes less relevant over time unlike endgame and middlegame knowledge.

FWIW, there was some guy on the newsgroups, a German I think, who was offering for sale his 500 page opening rep, all neatly typed and meticulously organized. I'm sure that reflected quite a  lot of work but I doubt anyone would pay for someone else's repertoire. It's personal, something you become intimate with over time, and otherwise doesn't work well.

Another point of having a repetoire is avoiding entire areas of theory. I always play the french defence as back (i.e. 1e4 e6) when white opens with e4. There is no panic for me to be familiar with the Ruy Lopez, Sicilian, Scotch, Petroff, Caro-Kann, Kings gambit, Four Knights, Alekhine, Scandanavian, etc,etc.

Yes, but some moves are much more popular than others. Especially since not all moves make sense, and people usually play moves that do!

For instance, if you as Black only prepare for 1.e4 and 1.d4, you'll encounter one of them in most of your games, by far.

I play 1...c5 against 1.e4, the Sicilian. Now there are a number of options; I need a line against 2.c3, but in the one I play there is a standard plan for both sides and we reach a position after move 10 quite regularly; I need to pick an Open Sicilian after 2.Nf3 and 3.d4 -- let's say the Classical, 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6; now Be2, Bc4 and Bg5 are popular for White, and I know a number of further moves after each. There are a few more possibilities, but I've seen them all several times as I've been playing the Sicilian as my answer to 1.e4 for like fifteen years now.

Similarly, there are probably like ten common answers to 1.d4 -- say, the QGA, QGD, Slav, semi-Slav, King's Indian, Grunfeld, Benoni, Benko Gambit, Nimzo Indian / Queens Indian, Dutch. It may seem like a lot of work to prepare for all of them, and I guess it is. But I play 1.d4 in all of my White games! I see all of them with some regularity.

All that said -- unfortunately, knowing them is a fun hobby, and I usually know the opening better than my opponent (OTB), but that usually has hardly any effect on the actual result of the game. That's decided on picking the right plan a few times in the game, tactical oversights and endgame skills.

Openings are like a maze. You run for a bit, BANG!! Hit a wall. Ok, turn this way instead, run run run BANG!! Hit a wall. And over and over again. Studying a lot of games from the same opening system will let you know where more of the walls are, so you don't go BANG so much. There may be some little trap doors, or faux walls, but for the most part, the walls stay the same. If you try to draw a map, you will fail, so just keep your head up for walls.

Not true at all, while there are a lot of theoretically possible ways to start off the game, only a small fraction of them even begin to make any sense. You will definitely see the same opening positions multiple times in your playing time...especially if you've studied some openings so you know how to transpose into lines you prefer.

False dilemma here (or rather, a dilemma with a false conclusion). For the openings you've studied, you will have the advantage of being on familiar ground. For the openings you haven't, you can just play by general opening principles as you mentioned. Learning openings can't hurt you at all...well, except by making you use up time studying them. ;)

I think you may need to either play more chess or keep a better record of your games. ;) While every game is different, the opening parts have been well-studied and it's worth taking a look at the theory...

And that is precisely another reason why you should study openings, since an opponent who knows it better than you can lay simple book traps and you'll just waltz into them.

I agree with you on this point though, sometimes an opponent will spring a novelty that looks to me to be weak but I can't capitalize properly on it. I do wish there'd be more explanations of why a certain move is bad, but I guess the amount of time the grandmasters have to explain things is limited. Hence the threads I started on the Marshall Defense and the response 4. ...Ba6 to the QGA. When the grandmasters aren't available, just ask your friends who are better than you. XD

I have found that my way of playing/style of playing tends to make some openings and positions rising from those openings easier to handle and play. That's why i believe when we are decent enough at chess we can start working on openings that do give us better results then others we tried out. For eg; if your aggressive u look for openings and variations of openings to support our natural way of playing and the same goes for people who like more solid positional sorts of games. That's my view on it anyway.

This is so true, very few books explain why bad moves are bad. An excellent book that points out bad moves is Tartakower's classic 500 Master Games of Chess (not sure if this is available in Algebraic Notation). In his charmingly verbose way, he points out "of course not 6... Nd5, because......." This book tought me more about openings than any other.

Not yet it isn't available in algebraic. It's one of the great classic collections and it's about time it get a modern edition--and in a binding at least as good as the Dover please.

For the uninitiated, it's one of those "desert island books" that if one were stranded they'd choose to take with them. 600+ games including the ones that appear in the notes, from Philidor to the 1940s.

Would this be a good book to learn about the openings?

Yes, I think so. The book is arranged by opening and by variation. If a student willing to work was also armed with a single-page summarization of the opening principles, there's no reason his understanding wouldn't surpass that of most of his peers who pick up specialized opening monographs and commit to memory lots of variations.

The only drawback, of course, it's a little dated. The 500 games include less than 20 Sicilians, if my memory serves. Thats probably the reason I don't play Sicilian.

In my first tournament 2 of my 3 games as white followed the same opening for more than 5 moves :P.  ... It happens, a lot :).

I have to strongly disagree with your comments about how openings are not important to players below 2000 elo.  That's about what my OTB rating is and I can tell you that the point of the opening, generally speaking, is to get you into the middle game in good condition.  If you're constantly improvising your way through the first part of the game, say moves 5-15, depending on what types of openings you play, you are always at serious risk of having a very poor game by the time you've barely gotten your pieces out of the box/bag.  The study of a few general purpose openings like pirc/modern and Kings Indian Defense/attack will get you several moves into the opening with out much trouble for the most part. And, as you gain experiance with those few openings you'll begin to learn where the danger is to be found, thus deepening your understanding of that opening "book".  The origianl poster really shows off his ignorance, which is what inexperianced players do, with his opening salvo here.  Hopefully he'll watch, learn and stop getting stomped as much as he probably is in the opening. 

Btw, for people who are beginners and looking for improvment, I give the two most important rules for surviving deep into a chess game:

1:  Don't give a way your pawns or pieces.

2:  An attack on the king is usually best met by a counter attack in the center.

This is an excellent point and one that is neglected. When I was a youth, I had a good grasp on opening principles and was a reasonably sensible player (I didn't have silly tactical mishaps for the large majority of the time), but the biggest source of my losses was coming out of the opening with a bad position. You can rely on general opening principles but if your opponent knows the right moves in the system he's playing, it can be very hard to match his book moves with just brainpower alone.

Now I know some theory and I very rarely come out of the opening with a bad position. This really, really helps. It's said that at levels below master it's middlegame mistakes and technique that will probably decide the issue - this is a fair point, but if you're in a bad position out of the opening it's much more likely that it's YOU that will make the errors, because it's much easier to err in a dodgy position than a good one.

If you follow the book moves of specific openings you are comfortable in then when your opponent deviates you would ususually find yerself wif a positional advantage

To the OP, learn the critical lines of an opening but make sure you know the ideas behind it. If a (good) opening book doesn't look at a move, you should usually be able to understand why if you understand the ideas of the opening or variation. If you don't, maybe you have the wrong book.

You don't play much chess do you?

Let's examine the simple math for a moment.

Yes, most moves in any given situation are bad, but let's assume that there are roughly 3 good moves for each step of the opening. The first five moves of an opening are actually 10 moves because there are both black and white moves. That means there are 3^10 good openings in the first five moves of the game, which is 59,049 openings. If you play two games of chess every day for your entire life, it will take you 81 years to go through all those openings.

I hate to say it, but people who swear that they play the same opening moves over and over again are just lying. It's mathematically impossible.

Of course, there are more than 60,000 people worldwide playing chess every day, so every one of these openings is played all the time, I'm just saying that for any given individual the chance of playing the same opening time after time is basically zero.

Opening moves get selected in no small part by fashion, so naturally they get repeated.

Do us all a favour and don't try to act like an authority on something you actually know nothing about.