I love to include shots using selective focus to isolate subjects in every assignment whenever possible. I do this generally by using my lenses' widest apertures.
In my sessions, this technique is useful in telling a story.
Selective focus can also be used effectively by focusing on the subject. Shooting through an object, thereby framing the subject, or again, to tell the story.
If you are not shooting manually, you may use the Aperture Priority setting on your camera (A on Nikon, AV on Canon) to achieve this effect. Select the lowest value (i.e. 2.8, 4.0, 5.6) and focus on what part of your image you want to be sharp. It's a bit more challenging to shoot through objects, but with some practice, anyone can accomplish this task. Happy New Year! And Happy Shooting!