This is how you draw a draping. I chose a dress which is very, very complicated and very, very draped to dive in full steam with.
First, you want to get your outer silhouette dealt with. Think about what your shape is going to be. Always when you're doing something draped you have almost like bubbles and squiggles at the outer silhouette of the garment which you can establish before you even make your lines. Then you carry your lines down, carry your lines down. You kind of want to be fluid, because draping is fluid.
Then, this dress that I'm drawing here in particular drapes from the hip, a corseted wrap dress. I just carry my lines directionally, because you want to do it in the direction in which you want the draping to happen. On this particular dress the draping comes from both directions. It's coming from underneath and it's coming from the overlay of it which is the upper layer.
First, let me finish out this upper layer. See what I mean? When you have draping happening you're going to have a squiggly line on the outside of your garment where the draping ends. Every time that you have a little squiggle you want to just carry that up, carry that up. It's kind of the same thing as pleats or folds.
I'm just going to finish up by creating the bottom of my gown. It's the same thing. Follow up, follow up, diagonally, just be fluid with your lines. Whatever, worry about the shoes later. We're only worrying about draping right now. Those aren't the best shoes I've ever drawn, but what are you going to do.
Alright. That's pretty much it. That's how you draw draping. This particular gown I've already created. This would be a photo of the finished product.