Emphasis

Contrast:
The red flowers are a major contrast to the gray skies and green stems.
http://fineartamerica.com/images-medium/hot-cold-contrast-1-floriana-barbu.jpg

Isolation:
The lonely umbrella is the sole focal point on this beach. The sand, water and sky
all pretty much blend together leaving the umbrella to stand out.
http://fineartamerica.com/images-medium/blue-isolation-trisha-lambi.jpg

Placement:
The stem and petals of the flower draw the eye to the center of the
flower which is the focal point. The blue sky and the flower are contrasting
which also help the lines draw the viewers eye.
http://gmuhs.wswsu.org/Art/003CF91A-000F58E8.14/Jannie%20hale%201.jpg

One Element:
The lighting and the color of the child's clothing help to make the child the obvious
focal point in the painting.
http://bsullivan35.files.wordpress.com/2009/10/matteson_scarlet_letter.jpg

Absence of focal point:
The blurred image of the face make for an absence of a focal point.
http://kaganof.com/kagablog/wp-content/uploads/2007/06/index_r1_c3larger.JPG