Ultimately, slow shutter speed photography is a fun way to take cool, unusual photographs. It's not for portraits, classic landscapes or sharp action shots. It's for light painting, and capturing the essence of motion through the art of blur. To take those kinds of shots well, usually you'll want to employ all the tips we've already been through. Keep the camera steady with a tripod. Use a timer or a shutter release. Shoot at night.
Once you've gotten those basics down, experiment. Try shooting during the day with neutral density filters to cut down on the brightness. Even with a camera attached to a tripod, adding movement to a shot can affect the motion blur in cool ways. Try panning to follow a light or zooming to blur different parts of an image. Use different apertures to play with the amount of light reaching the image sensor.
A long shutter shot can last for just a few seconds or be much longer. The light your camera catches will look very different based on that exposure time. Seek out inspiration online and try your own hand at light painting or nighttime urban photography!