I know there are different weights for silicones, and wonder what difference it makes in products, for instance what's better for hair vs. skin, and what difference do the different weights make? 

I found the article about Dimethicone Copolyol not weighing hair down, and a hefty article about new silicones here: http://www.cosmeticsandtoiletries.com/formulating/category/antiaging/34408409.html?page=1

I'm hoping there's a simpler answer that can help sort out the basics.  Anything about clues for reading labels would be a nice bonus too, for instance I always remember "ampho" generally means amphoteric, etc.