I am playing the QGD as black donno what to do against the exchange variation.

How do you tackle the exchange variation. Where should my light squared bishop go. Where should my queen's knight be posted?

I think almost all vhin said is wrong lol.

Pawn goes to c6 in the exchange variation, meaning the knight will develop at d7.  I think Black aims for bishop at f5 if possible. In the diagram above, Black also has the option of capturing with the knight rather than the pawn. Then e4 can be met by Nxc3 followed by c5, which is the semi-Tarrasch, and seems to me a nice straightforward line to play. 

A lot depends on White's approach what black does against the exchange.

Black also has a couple of options.

The main line goes 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.cxd5 exd5 5.Bg5 c6 6.e3 Be7 7.Bd3 O-O 8.Qc2 Nbd7 and now a lot depends on 9.Nf3 or 9.Nge2.  In both cases, 9...Re8 and 10...Nf8 is the main line.  If he goes to f3, you are looking at the Minority attack, which is harmless now a days, or opposite side castling.  On e2, you have the central attack and opposite side castling.

If Black wants to play "outside the box", there is, after 5...c6, another option for Black.  If memory serves me right, it is 6.Qc2 Nh5 and 6.e3 Bf5 7.Qf3 Bg6 8.Bxf6 Qxf6 9.Qxf6 gxf6.  Black has the Bishop pair, White has better pawns.

9 out of 10 people castle short in the Nge2, maybe poucin (vive la france!) has some lines for OP here.

Kaidanov made a video series on chess.com on queen's gambit declined

Some links (just the ones with exchange queen's declined) :

https://www.chess.com/video/player/the-complete-queens-gambit-declined-the-basics2

https://www.chess.com/video/player/the-complete-queens-gambit-declined-classical-carlsbad-for-black

https://www.chess.com/video/player/the-complete-queens-gambit-declined-a-modern-treatment-of-the-carlsbad-for-black

This last was tried several times in Kasparov vs Beliavsky candidate match, and eventually shown to be a bit dubious by Kasparov. Would surely hold-up in club player games.

Recently have become convinced by the semi-tarrasch option (4... Nxd5), with usually Nd7 to avoid the classic attacks after d5, with the knight misplaced on a5. In OTB in the resulting wide open positions not so easy for human players to calculate to maintain equality, but objectively speaking it is hard for white to prove anything.

The quality chess book playing 1.d4 d5 explains very well - Employing the ...Be7/Nbd7/Nh5 Kramnik recipe, usually with h6 flicked in, and waiting to castle until white commits his king first.

This looks really interesting deirdre, can you additionally post some good black games in the Botvinnik central attack? That would be cool                                                                                                                   Thanks also pfren for mentioning that kramnik-nisipeanu game, i dont understand why kramnik let his pawns get shattered all over the place

At the risk of being compared with Yigor, I looked at some database statistics.  In games where both sides are rated below 2100 in my database, White has a ridiculous score with the Exchange variation: 51% wins and 24% draws.

This makes sense, because White has a (small) structural advantage: an extra pawn in the center and an open c-file that faces a potentially weak pawn (especially after the minority attack).  Black's counterplay is a bit more nebulous, and a single mis-timed move or inaccuracy can let White completely take over with little risk.  Considering below master level is by definition filled with mistakes and inaccuracies. it's no wonder why White performs so well.

In short, you are not alone in finding the QGD Exchange hard to face.  The Kramnik idea above seems like a good attempt, or perhaps ThrillerFan's more imbalanced suggestions as the bottom of his post.

Possibly of interest:

First Steps: The Queen's Gambit

https://www.newinchess.com/media/wysiwyg/product_pdf/7652.pdf

The Queen's Gambit Declined: Move by Move

https://www.newinchess.com/media/wysiwyg/product_pdf/7743.pdf

Playing 1 d4 d5

https://www.chess.com/blog/pfren/playing-1-d5-d5-a-classical-repertoire

https://www.qualitychess.co.uk/ebooks/Playing1d4d5-excerpt.pdf

Play 1.d4 d5 2.c4 e6!

http://www.chess-stars.com/resources/contents_Play%201.d4%20d5%202.c4%20e6!.pdf

I thought the Beliavsky game was very similar to one of your examples, but anyway I don't have much problem with the approach.

Club players have always played stuff like 1.d4 d5 2.c4 e6 3.cxd5, it shows they don't know what trying to achieve by the exchange. There are lots of ways to play when Bc8 isn't being restricted. The mentioned book Play 1.d4 d5 2.c4 e6! covers it, and similar tries, if need it, which people shouldn't really if have some understanding of the structure.

Here's the Be7 Nbd7 Nh5 thing Pfren and TwoMove mentioned.

The annoying thing about the exchange (as with most exchange lines) is if I want to play for a win as black... that's something GMs who win tournaments on +2 after 80 rounds don't have to worry about

yes that would be nice, i kinda struggle being on the black side here

Thanks alot Deirde, that was helpful, the 4...Be7 line seems to take the sting out of the position

@ Deirdre :

1.d4 d5 2.c4 e6 3.c4xd5 is innacurate for white because black can develop differently.

The development c6-Bd6-Nge7 being quite effective and easy to play for black.

For example, here a game i witnessed in a tournament i played.

I made some lectures in my chess club on minority attack (especially how to defend/fight against it), and I used this game to finish it, with the idea 15...cxb5 and a5 to get a useful passed pawn, combined with the usual attack on king side.

I've let my commentaries, all in french so my appologies for those who don't speak/read this language.

I used 3...Be7. There are some annoying lines still. Let me try to remember... something like these

So IMO it's better to copy Kramnik... but again you have to be happy with a draw as black.

And unlike Kramnik, you'll probably be playing people 200-300 rating points below you now and then

 What do you think about this  attempt preggo, little bit counterintuitive to move the B twice and very rarely played

Queen cant take on b7  on move 10 because Nb6,Bc8 trapps the queen thats quite cute