Bokeh brings to mind out of focus point source lights in Christmas pictures where the effect is rounded well defined highlights in the background. However Bokeh is more than that. It really is the out-of-focus areas in an image. There are several ways to control Bokeh. The main method is Aperture control. The wider the aperture is open the shallower the depth of field, giving more Bokeh in the foreground and background. The second method is to reduce the distance between your camera and the subject. This will reduce the depth of field as well. The third method is by using longer lenses, which have inherent shallower depth of field than wide angle lenses.
The object of this challenge is to think about Bokeh when you take your image by putting your camera preferably in Manual mode and use Aperture, Shutter Speed and ISO to experiment. Alternatively use Aperture mode and let the camera decide the other two variables.
Here is a video with a good explanation and some examples.
Bokeh can also be manipulated in post processing. Especially the smartphone apps are very good at this. Here is a tutorial showing how it is done in Lightroom.
For those of you who might be interested in artistic Bokeh, there is an interesting tool that fits over top of a lens with a number of movable prisms and filters. Here is a tutorial that shows the effects.