There are a lot of different ways to draw. Most of the time we use lines to create the basic shapes and even to indicate where shadows are. There are other ways to go about it though. One of the most time consuming yet interesting ways is to use dots.
Using dots to create an image (in the drawing world) is called stippling. If you were painting or using colors it would fall under the pointillism style. Definitely an abstract way to go about creating an image, but beautiful, in my opinion.
This past year I have done several drawings using stippling. While very time consuming, the results look very unlike any other drawing style. It is indistinct when looked at up close, just a collection of dots. When viewed at the correct distance the image is reviled.
Like most other drawings (or any art) you start off with an outline of each shape or section. Make notes or some way to tell yourself how dark each area will be. Having decent sketches and reference photos/images for the illustration are going to be a big help.
First I look up some reference photos. I like to check for textures, positioning, layout, lighting, and other things that make a drawing come to life. Google is great for this. Lots of images with different view points. This is also a good time to pick you medium. All the samples I have are in pen. You will need to make allowances for the size or color of your medium. That will dictate how close your dots need to be in order to achieve the effect you want.
Second I sketch out the layout in my sketch book. Most of the time that is all I do. If I have trouble with any of the shapes or textures, I will do some practice, but not often. (No images of this. I do not usually document this part.)
Next up is moving to the nice medium. Sketch out your design on your paper (or canvas.) Make sure to mark areas that will need extra attention. Fine but defined lines, almost black or black areas, and solid white areas, are good to mark well.
Pick a spot and get started. This is going to vary depending on the piece and you. I like to start on the key object (s), once that is done I work from the top down.
Like anything the key is to have fun and take breaks. Lots of breaks. Ever time you start going cross-eyed or have trouble seeing the area you are working on, take a break. Make sure you eat. Shaky hands are not helpful when stippling.