I like to do the following exercise:
1. Make two dots, one above the other, approximately an inch apart.
2. Connect the dots using a scribble. Any sort of scribble will do, but try to use some rounded scribbles instead of making it look like a polygraph.
3. Draw whatever you see. I like to do faces, and did faces in this practice. You do not need to limit yourself though. If you see something else, draw it up!
This gets your mind thinking more creatively. The more often you do it, the better you get, just like doing curls with weights. This gets your mind thinking outside the box and seeing things that you did not see before. It may come slowly, but it is a worthy time consumer, if you are interested in drawing and want to get better. Here is a video of me drawing up some faces using this method:
Here is the end results:
Sometimes, a friend and I will fill up pages with scribbles and swap them, drawing whatever comes to mind. You can make scribbles in any way. It does not have to be in a vertical line. You can do it however. Just embrace the randomness and make it your own master piece.