1. I start with a light sketch/outline. In this way, I can easily erase it. (Outlining is very hard, it needs time and more practice to achieve same forms and shapes in the image you wished to draw.) I always start outlining from the eyes to eyebrows, face, nose, mouth then the hair. (Im comfortable in this way. You can follow or have your own techniques.) 

2. I make sure the pencils tip are sharp at all times. (Get a very good manual sharpener) Starting at the right is my first step, from the eyes to eyebrows then the skin. I lightly start laying the general tones of the skin carefully. I let the tip glide over the surface smoothly and making sure I don't push it hard to avoid large strokes.