The composition is the placement of elements in a manner which pleases the eye.
Compositional techniques help in creating an aesthetically pleasing art where the elements are balanced.
The composition can be achieved with several techniques such as
Divide the image into a grid of 3 rows and 3 columns.
If we place the essential elements of our object on any of these lines then our composition is more pleasing to the eye.
In intersection points of the lines are also very good places to place essential elements of our elements.
In this painting by John Singer Sargent, there are 2 essential elements.
The aeroplane which has crashed is in the background and the people in the foreground.
The painting was created in 1918 and has a view over the fields with a crashed aircraft. Two labourers are gathering the crop into bundles. A man is working with a scythe busy in his work.
In this painting, the crashed aeroplane is placed at an intersection point at the upper right portion and the figures are placed at an intersection point at the lower-left portion.
One of the most famous paintings by Vincent van Gogh, The Starry Night uses the rule of third.
The focus is on the swirls on the top and to the tree.
Having an odd number of elements instead of an even number makes the art more pleasing to the eye.
The idea being that an even number of elements would produce symmetry which would appear less interesting whereas an odd number of elements would make the art more dynamic.
The rule of space relates to movement, it is an illusion created to indicate movement. For instance, if the artist draws a runner then adding white space in front rather than behind would indicate movement.
If our elements contain people (who are walking or running), cars or anything else which is moving it is important to give them space to move.
This is the rule of space.
The rule of simplification says avoid to the clutter, make the main elements more bright while simultaneously increasing the detailing.
Whereas for the background increase the darkness and decrease the detailing.
This will bring the main element in focus.
This painting done in 1884 by John Singer Sargent is a portrait of Edith Vickers and her husband Albert.
The flowers, glass and silver are beautifully painted with great detail. Edith is painted with great detail whereas her husband is only partially represented.
The detail in the background is very small compared to the rest of the painting.
Elements placed in perfect order by size and distance are not pleasing to the eye.
Consider this placement.
Now let us rearrange this order and place it differently
Avoid patterns to create a natural composition.
Avoid anything that looks staged, uniform or symmetrical.
Of course, rules are meant to be broken and there is no rule which says that your composition will look un-aesthetic if you have broken these rules. Maybe you can make your own rules.