The neck and cap is developed in similar manner. The entire drawing is constructed from just two basic shape the rectangle and oval. These are two shapes that is most often found in drawings. You must practice making these shapes. Use light clean stroke to make the lines. It can be darken further later.
Next comes the shading part. Shading establishes dimension and gives the realistic look to the bottle. Here the pencil is held low and the side of the lead is use to create the shade. The process is called "burnishing". Different pressure creates different shade.
You can now find similar object and try drawing it. I will add more practice and methods in the next post.