Taking advantage of people who don't follow the "rules"?

I play against a lot of people who are self taught and don't follow the rules of sound openings.  I routinely play against people who say as white I'm opening with the Ruy Lopez, when I play Bb7, they will play a6.  How "bad" is that move on their part?  Is there a way to exploit people who seem to attack too early in the opening?

If their counter to your opening seems awkward, finish development quickly so as to try and get a tempo advantage on them. You will be able to attack quicker and with a better standing/position. If they "attack too quickly", watch for blunders. Many lower rated opponents may make one.

Keep in mind this is all assuming your opponent plays badly in the opening. Their "strange" opening has a good chance of being sound if they play it right, or could have some gimmick to it that you don't know about.

You mean like this?

That's actually a pretty sensible move in this particular position. The problem with non-developing pawn moves in the opening is that they waste time without contributing anything to your position. In this case, however, this principle doesn't apply because:

• It threatens the white bishop which then has to move. Since White is forced to move his bishop again and thus waste time, Black hasn't really wasted any time of his own. (If that makes any sense.)
• White will probably retreat his bishop to a4 to keep the potential pin against the knight on c6. With the pawn on a6, Black can play b5 at any time, kicking the bishop yet again and breaking the pin.

Where's Bb7 in that diagram, HappyUngulate?

If you have a good grasp of basic opening principles you'll be able to deal with substandard and unorthodox openings without having to worry about memorizing "refutations" (if there are any) for every single bad opening you face. And believe it or not starting to learn basic endgame principles will help you steer the game into favorable endgame positions for yourself and avoid going into endgames with weaknesses you could have avoided in many cases such as doubled pawns, isolated pawns, kings on h1 or a8, "bad bishops" etc etc. These links should be helpful, as well as some advice from 2 of the greatest GMs in history

http://www.chess.com/blog/NimzoRoy/chess-opening-principles?_domain=old_blog_host&_parent=old_frontend_blog_view

http://www.chess.com/blog/NimzoRoy/endgame-faqs?_domain=old_blog_host&_parent=old_frontend_blog_view

One doesn't have to play well, it's enough to play better than your opponent.  TARRASCH 

When you don't know what to play, wait for an idea to come into your opponent's mind. You may be sure that idea will be wrong. TARRASCH 

To improve at chess you should in the first instance study the endgame. CAPABLANCA

In order to improve your game, you must study the endgame before everything else. For whereas the endings can be studied and mastered by themselves, the opening and middle game must be studied in relation to the end game.  CAPABLANCA

Nowhere. I wasn't aware of any line in the Ruy Lopez where White moves his Bishop to b7 early in the game, so I assumend that the OP meant Bb5 – especially since a6 is the most common answer to that move. I wasn't entirely sure, though, hence the question "You mean like this?"

 I'm not understanding Bb7 either, so you're probably right that it's Bb5.

Yes, Bb5.  Sorry.

FYI The Zaitsev Variation of the RL goes 

4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 d6 8.c3 0-0 9.h3 Bb7

An alternative to 7...d6 is 7...Bb7. This is  the Trajković Variation.

I'd guess these revelations are probably irrelevant if we're talking about opponents who barely know how to set up the board correctly and have never heard of en passant...

Yes, but we're talking about White playing Bb7, not Black.

NimzoRoy: Yes, but he wrote Bb7 and a6, and both can only be played by black in the opening, so it is clear that he meant Bb5.

whatever move or moves anybody plays in the opening just make sure yours is better and not a blunder...forget the principles and learn by playing 

So the question is:  what do we do against somebody so iconoclastic that they play the main line?! lol

Any 1100 player will tell you those are the easiest lines to win against.

play outside the 'book'...remember majority of our opponents are nearer idiot rather than genius when playing chess...your opponent may even have a rush of blood to the brain and make an original move(for them that is)...then they may feel the thrill of creative chess playing!

Sure!  Play 4 Bc4! (I remember a guy who used to do that, in fact)

How do you know that they don't follow rules? And which rules?

I don't know if GM follow rules. If you can't take advantage, it should mean either you are not that good and they are better. Or you don't know that particular line.

There are no hard rules in chess. They are only some guides.

Maybe they want to try out a particular move against you. And maybe you follow the guides (since I don't call them rules) from books, you are in lost when they make their own moves.

I think they are creative. Maybe they will lose in the end, but thumbs up for their creativities, even if they lose.

Keep playing and keep improving. GL.

If a guy were black and the game goes, 1. d4 Nf6 2. c4 and 2. ... a5?!. He doesn't follow the guides. But can you find a way to win? If you can't, then he is clearly better, cause he make a very minor mistake and you just can't take any advantage.

I feel at the beginner level(atleast till a rating of 1400, even higher) one can play anything one wants in opening and just respond to your opponent's move. 

I don't follow any opening principles and have a rating of above 1400 in bullet,blitz and standard,not bragging just stating the facts.

ha....we're all amatuers