How to improve SKETCHING

In short, by practice

See a piece with different parts.
I find taking your photos or finding pictures in books/magazines/online and sketching them to be EXTREMELY helpful. It’s also a great way to get dramatic but unchanging lighting.

Looking at things and even doing a rough sketch is practicing. Print out a picture and trace it. Practicing! Challenge yourself with different studies. It’ll round out your art.

Let’s look at an image:

What do you see?

A hand. Fingers. A pointing finger.

Look again.

Everything can be broken down into a series of simpler shapes.
Light (yellow), shadow (green), colors, and other smaller pieces (red).

If a scene/picture/project/whatever seems to be too daunting or just plain overwhelming, find the shapes. They make things simpler and easier to tackle. They show the relationship between the different parts, improving your ability to judge distances and lengths. They can also bring a greater sense of depth to your images when you find the shapes cast by light or shadow.

Combine the practice studies I mentioned with this shape method.

It makes a difference.

Best of luck!         via-quora