Using the Golden Section
 

To locate the center of interest with the Golden Section: Divide the height of your canvas by 2.62 and determine a horizontal line through this point.

Then divide the width of your canvas by 2.62 and draw a vertical line through this point.

The intersection of these two lines is a magical spot for your center of interest.

For example, the center of interest on an 8 1/2 x 11 inch standard sheet of typewriter paper would be determined thus:

8.5 divided by 2.62 = 3.2 inches and 11 divided by 2.62 = 4.2inches

Example
 

The intersection of the two lines described above is the exact point of the kiss in my painting below.

Of course there are many valid ways to compose a work of art, but I think this painting works best using the Golden Mean.