I have very fine and thin hair- thin strands and not a lot of hair- what's the best shampoo/conditioner?

One thing that will really help is NOT conditioning your roots. You always want to use conditioner only on the bottom half of your hair strands because it does cause hair to fall out. Not to mention makes roots look greasy. This will also add lots of volume to your hair. Try using volumizing shampoos. My personal favorites are Pert Plus and Aussie Aussome Volume shampoo. Pert Plus is a 2 in 1 shampoo+conditioner and you don't need much conditioner. Both my sister and I have been using it since we were kids and I can't begin to describe the amount of compliments and questions people ask about our hair. Hope this helps!