Watch for whatever folklore claims the ghost does. There is no way to present a tidy list of what to expect. It's what you don't expect, that is usually the ghost. You can detect ghostly energy with an EMF meter. The compass needle swung the same way, every time we tried it.
Cameras also record ghostly energy as orbs and other oddities, called anomalies.
To take successful ghost photos, check my website for Ghost Photography 101 . Avoid pointing your camera towards a light source, or anything that might reflect your flash. It could be a whispering sound. Or a strong impression of intense emotions, including fear or rage. If you've been near a ghost, and kept a level head to rule out natural explanations, you'll have no doubt about what happened.