You can often tell the 'official' right side by looking at the selvage. Sometimes it's blatant, as there will be something printed along it, but otherwise I go by the 'pinholes' made by the manufacturing processes. The way I see it [excuse me if this is a crap description but I'm not very awake yet] the holes make little 'dents' on one side, and'peaks' poking towards you on the other. The dents are usually the right side
I thought it was the side with the peaks that is the right side!
The holes are formed by the machinery making the fabric; little pins sticking up at the edges of the rollers are what make those holes, and if there is any printingto be done it goes onto the side of the fabric which is facing away from the rollers and so has the peaks around the holes.
Calling Raving Doll - what does Muv say about this?
I agree though that the right side is the side you like best, and the two sides can be used for subtle contrast. Crepe back satin is the classic for that. Just be sure to mark the fabric with chalk on the wrong side if it's difficult to tell, for instance you don't want sleeves looking very slightly different to the rest of a garment.