Hmmm, I don't know that I've ever really undertaken the idea that one can train for symmetry. How big of a difference are we talking? 1/4 inch, 1/2 inch... or do you look like a human fiddler crab with one huge arm and one shriveled up little nub?

Everyone has some asymmetry. I have an arm bigger than the other, thighs, calves... etc. But I doubt very much that anyone looks at me and thinks "freakishly lopsided." Heck, the "greatest" bodybuilder of all time had a BIG difference in his biceps (Arnold).

If it were me, I would probably limit my work by what my "weak" side can do. The problem there is that while my left arm is smaller (by maybe a 1/4") it is also stronger. So I've never bothered. Nobody is perfect, and unless you think there is a career in bodybuilding at stake I would say that you are going to see better results from coming to grips and appreciating who you are, rather than trying to develop something that may never happen.