There are numerous approaches or "compositional techniques" to achieve a sense of unity within an artwork, depending on the goals of the artist. For example, a work of art is said to be aesthetically pleasing to the eye if the elements within the work are arranged in a balanced compositional way.
However, there are artists such as Salvador Dalí who aim to disrupt traditional composition and challenge the viewer to rethink balance and design elements within art works.
Conventional composition can be achieved with a number of techniques:
Rule of thirds
The rule of thirds is a composition guide that states that arranging the important features of an image on or near the horizontal and vertical lines that would divide the image into thirds horizontally and vertically is visually pleasing. The objective is to stop the subject(s) and areas of interest (such as the horizon) from bisecting the image, by placing them near one of the lines that would divide the image into three equal columns and rows, ideally near the intersection of those lines.