Don't strain when you rack from carboy to carboy! You can strain the first time you put your wort into the carboy or plastic fermentor, but after that, no way. Just rack the beer (siphon) from above all the junk ("trub") on the bottom. Your beer will clear up that way, and you won't oxidize it. Oxidizing your beer by aerating it after fermentation starts will ruin in.
I just throw my hops in for dryhopping, but somepeople like to use sanitized hops bags. The choice is yours. If you use a bag, add some sanitized marbles to weight it down, otherwise it just floats on top.