Bokeh is the Japanese word for “blur” and can lead to some common misconceptions about the effect. I’ve heard bokeh explained as, “Just a blurry background.” It’s tough to bite back the annoyance that arises at such a simplification. A Rembrandt is not just a pretty painting and bokeh is more than blur.
More specifically, bokeh is a highly stylized background created by selectively blurring parts of the picture in a way that highlights the subject. Not merely a blurred background, but one that pops with colors and patterns. Good bokeh doesn’t always require a subject, sometimes just the pattern of lights without a subject is just as appealing.
You don’t need special equipment to achieve bokeh, but it helps to have a fast lens, like the Nikkor 50mm f/1.4 and a selection of ND (Neutral Density) filters. Those help achieve the lower f-stops you’ll need and they’re also handy for shooting video where you have less latitude in shutter speed selection. You don’t have to use ND filters, you can also experiment with your camera’s Aperture Priority mode (the “A” setting on Nikon, “Av” on Canon) and let the camera set the exposure, but I like the results with ND filters a little better and I can still lock a subject in motion.
For the inspirational bokeh, look for sunlight filtered through leaves and foliage or bright pinpoints of light in the background.
Get as much separation as you can between your subject and the background.
As far as I know there are few cameras with an “auto bokeh” setting, so you’ll want to use the widest aperture (lowest f-stop) your lens can achieve.
If you need fill flash, you’ll be limited to flash sync shutter speeds, which may or may not yield the desired f-stop. Times like these is when you may want your neutral density filters.