Trick, Photography Book - How to believably blur backgrounds in Photoshop! (Without the funky edges and halo effects! Photoshop tips. - Now YOU Can Create Mind-Blowing Artistic Images With Top Secret Photography Tutorials With Step-By-Step Instructions!
Use a brush to "paint out" the portions of the image that should disappear. The mask itself is white, so it is easy to remember that "white reveals and black conceals". Use a soft black brush to paint out the background.