Most people do not want to accept the possibility of the paranormal. The possibility of things existing that cannot be explained is too much for some people to handle. This is why those bumps in the night are often contributed to alarm system motion detectors and pets, or similar excuses.
Pets
Yes, many people use pets to explain those strange sounds, but you can tell the difference. Many pet owners have seen their dogs bark for no reason at all. Dogs have acute senses that humans simply do not possess. You can use a dog to help pinpoint the location of a visitor that has passed on.
Motion Detectors
Many alarm systems come with motion detectors and cameras. These tools are not designed to capture the supernatural, but they may be able to detect the effects associated with such visitors. Many experts believe that ghosts are some form of energy, even though science attempts to disprove this all the time. Energy is constant, and it powers the human body, which is the basis of the theory.
Some ghost hunters use this assumption to justify the use of a camera. The energy that ghosts give off might create disturbances in the atmosphere that your camera might capture.
Of course, some ghosts are capable of moving things around in the real world. This is another reason why you want to make sure that you have a functioning alarm system complete with motion sensors and cameras.
Poltergeist Discovered
You have your pet, alarm system, and your intuition to help you figure out if an entity is in your home. You may not find anything for some time, but at some point you confirm that something is lingering in your home. Now, you might be wondering what you should do about this phenomenon.
The first thing you should do is make sure you really did experience something supernatural, because expert ghost hunters will want to rule that out, first. For example, make sure sounds are not coming from rodents or old pipes. The next thing that you want to do is keep a journal of events that have occurred in the house, including areas and times that you notice something suspicious.
The last thing you want to do is call a paranormal investigator to help you determine what kind of poltergeist you are dealing with. Show your journals and video footage (from your surveillance system) to your investigator. Make sure you mention that you used your pet to sniff out this poltergeist, too, as every detail is crucial for this type of investigation. These tips should help you figure out if you are dealing with something paranormal or not.