Just put an object in front of you and begin to draw it, draw it 100 times, and each time try to something different, be it the material that you draw on, what you use to draw with.
Take a photo of it and draw the photo, compare the difference of the drawing from reality and drawing from the photo image. yes there is a difference and this is why I say do not draw from a picture or photo.
Tips on how to draw negative space
Just look at what is around the objects that you plan to draw, and see them as the shapes that you want to draw.
Drawing negative with a putty rubber
Sugar Loaf hidden by a tree
I had lots of fun finding different views of the Sugar Loaf, but what I like best of all was how it was hidden behind the leafless trees in the winter