I spotted a picture of a young woman, and took her as an example for my exercise in my sketchbook. I chose a page which I had already prepared with an acrylic base, and started drawing with a black aquarel pencil. She was looking downwards so her nose was rather long and she had her eyes closed.
When I start I often think: Oh this is too difficult... I cannot do it. But for me just starting helps, especially when you use a light sketchy touch to your pencil so you can correct dimensions and shapes, until you find that it might actually work. This way the drawing turned out better than I thought. Also the acylic underground gives somes structure, and of course soft undertone, which I like.
I'd say: take out a piece of paper and begin!