Over time draping has become less difficult, but still a challenge. I am getting a good draping exercise by making a slip cover for my old couch. Newer couches have the over-stuffed arms that curve. My couch doesn't have this and I couldn't find a slip cover to fit. A custom cover is $$$. Why not do it myself (with help from a library book on slipcovers)?
I am draping the cover with a "muslin" of green broadcloth and an old sheet.

I just draped the arm and will be moving onto the deck next. This couch has the added difficulty of being a sleeper sofa. We would never have bought a sleeper sofa in a million years but it was given to us and so we use it.
This is the fabric for the couch, a great buy from Wal-Mart. Wal-mart carries upholstery fabric and the price is usually great. BTW, that is our gold rocker. Isn't it lovely?! Unfortunately, the style is too difficult to slipcover and will have to be re-upholstered by a pro.