Used Variety of Lines

Keep Your Pencils Sharp
Chisel-point or blunt pencils are useful for some techniques, but for most pencil drawing, keep your pencil sharp. Don't worry about 'wasting' graphite in the sharpener - better than wasting your drawing efforts! Brighten the point by rubbing the side of the pencil on scrap paper between sharpenings. If you need a darker line, use a softer pencil, and be aware that a softer pencil goes blunt quickly.
Use a Variety of Line:
When drawing lines, either in a linear drawing or within a texture in a tonal drawing, note that you can vary the weight of the line by lifting the pencil or pressing harder. This might seem obvious, but it is important, and most people don't exploit lineweight enough. Note the example above, which shows how lifting the pencil towards the end of the stroke can be used to give a grassy or fluffy effect. It can be useful to reduce the weight as the pencil is applied at the start of the stroke, rather than dropping it straight into full pressure.


(Source by - http://drawsketch.about.com/cs/pencilgraphite/a/pencildrawing.htm )