how do u play C G D barre chord?

Here some examples for the chords
C in barre: finger on the eight fret, and your fingers placed like you take the E chord.
like this:
x   x   x   x   x   x (fret 7)
o   o   o   o   o   o (finger setting on fret 8 and o stands for finger)
x   x   x   o   x   x  fret 9
x   o   o   x   x   x  fret 10
x   x   x   x   x   x  fret 11
To take the D chord in barre, you do EXACTLY THE SAME, POSITION OF FINGERS BUT now on fret 10, where your finger covers the strings on the 10th fret, followed by the same position of your other fingers: an E chord, just under your finger covering fret 10
G chord, where you cover with your finger the 3th fret and again E like in the other examples. You can do the same for A: finger pushing on the 5th fret, an again the E chord.
I really hope I could help but I will give you a site, where you can find a LOT of chords, you get the standard chord for G, but you will notice normal chords and what they call split-chords.
You will also see, on your screen after you "click" on let's say the A-chord, there is a get it: ckick on it and you will see the chord. BUT you will see on top A, and lower six little things; in fact giving you the opportunity to see 6 different ways to play the A chord.
www.all-guitar-chords.com a very good site to learn chords
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GITAARDOCPHIL SAIS: YOU SEE DIFFERENCE BETWEEN A STRING, AND A WOMAN's STRING

Hey reddevil,

If I'm reading you're question correctly, you're asking for the G, C, and D barre chord shapes?  If that's the case, just finger the open version of the chord with your 2nd, 3rd, and 4th fingers, and then when you move up a fret, barre any of the open strings with your first finger.  It should look like this:

C shape

e - 1
B -2
G -1
D -3
A -4
E -x

D shape

e -3
B -4
G -2
D -1
A -1
E -x

G shape

e -4
B -1
G -1
D -1
A -2
E -3

Let it be known that I can in no way play any of these in rhythm and I can barely play the G barre at all, lol.  If you haven't mastered the A and E shape barres, I recommend doing those first.

Hope this helped!

reddevil, as I wrote go to the site I advised, it is at first a little bit complicated, but you will see that everybody here is 100% correct.
Some chords are better, I mean easier if you play them in different "style".
See Jerome: he gives you exactly the same chords, but the finger positions are different.
So you have to figure out what position suits you the best.
Jerome's chords are easier to change faster than my chords, but I call this more a skill. Try the different ways for your chords in barre, and than you can make conclusions.
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GITAARDOCPHIL SAIS: BARRE IS NOT A BAR in RE

Well, the thing about this C G D progression is that  it's just a IV I V progression in the key of G.   The I IV and V chords of *any* key are always easily available to you within three frets as long as you're playing the E or A shapes.  The I and the IV are available without moving your hand if you're in the E form, and the I and the V are available without moving your hand if you're in the A form.   That's what makes the barre so powerful, particularly for rock and roll and modern pop.