Here's a photo I shot just now with the 18-55 to show the out of focus bokeh with the lens in question:
Note that "bokeh" is the
quality of the area out of focus, not the fact that it
is out of focus. "Good" bokeh is considered smooth, and is attributed to many aperture blades OR a wide open aperture that is therefor round, so the number of blades don't matter. "Bad" bokeh is considered jagged or jarring looking, and is caused by having only a few (typically 5) blades to control aperture. The bokeh is governed by the way the blurred area takes on the shapes of the aperture, so if the aperture is round, the bokeh will be round and thus smooth. If it's shaped like a stop sign, with 8 sides, it will be a bit less round, and therefore a bit more jagged looking. If it has 5 sides like a pentagon, it will be even more jagged looking. If you cut a little heart-shaped hole in some construction paper and cover the lens with it, it will produce heart-shaped bokeh in the out of focus areas, as shown in this tutorial:
DIY - Create Your Own Bokeh | DIYPhotography.net
The image I shot above has my aperture wide open at f/5 (at 37mm) so there are no aperture blades in the way to define a shape. The aperture opening wide open, even at f/5, is round and thus smooth. Look at the background just to the left of the words POP CORN, and you'll see the smooth round shaped bokeh produced by the wide open aperture.
As for HOW MUCH will be out of focus, if you want more just put plenty of distance between your subject and your background, and that's true for any lens.