Principles of painting and sculpture such as line and balance, and depth, perspective and form can be skilfully applied in the illusion that is bonsai.Attempting a representation of nature it is most useful to study trees and landscapes and absorb how these principles are expressed in nature.
At the same time we must keep in mind that which makes bonsai different from all other plastic arts: the fourth dimension of time.Visualising what the tree will look like in the future is a beautiful pastime and a key consideration in design. The computer can be an useful aid to visualising the future as can be drawings and photographs.

That trees are living things and interact with their environment are important guidelines for design.The various bonsai styles should be looked at as principles drawn from the way trees grow in nature. The species and the environment in which the tree is growing both affect the style.
Proportional guides,which should not be considered as written in stone, are as follows: The tree height should be from six to ten times its diameter at the base. The width of its canopy is often about 2/3rd. of its height and the depth of the tree's canopy is about 1/3rd. the height.
The pot is like a frame of a painting, and its size, shape, depth and colour has an important impact on the image suggested by the tree. In general the depth of the pot is proportional to the tree’s thickness at its base.

The links below explore key concepts in detail: