Trimeister: You're correct. You need at least two curves to create a panel. However , often you would like to create even more curves to make your cloth actually looks like cloth. For example - you dont want a shirt to be seamed together at the neck and arms.. ?

First make one curve (when finish, press Y instead of enter to repeat making curves), use "snap to curve" (hotkey C) and drag the startingpoint of the next curve to the very end of the first curve. Then make the new curve. Go on this way 'till its a closed loop (endpoint of last curve is exactly the same place as startpoint of the first).'

You dont need to make curves for more than half of the cloth. You can just dublicate -1 before you group the curves. Just make sure that the curvepoints are snapped to grid (hotkey X) where the mirroring will be done so that its still a closed loop.

And remember what duck said. All curves should be co-planar.