Being known for all the charity quilts I do, I get "gifted" with a lot of fabric scraps and boxes of fabric that people no longer want from their stashes. This being the case, I never know what has been washed and what hasn't. It just makes good sense to stay in the habit of washing EVERYTHING, so that it's all consistent. But, truth to tell, I would pre-wash even if it were just my own fabric. I like knowing there won't be future bleeding or shrinking going on when I've done all that work on a finished product. I use starch if I think it needs it, but just spray water if that's enough. I seldom use steam in my iron... even my very expensive iron tends to leak after a while... and spray bottles are cheap.
I don't iron my fabric straight out of the dryer.... I fold neatly and put it away, and then iron (yes, iron, not press.. go ahead and shoot me....) when it's time to start cutting it.