Have you had things go missing or ever noticed items in other places than where you left it.. ? You may be dealing with a Poltergeist.. If you are unsure of what a Poltergeists is it is a ghost that moves objects around..
It could be any item, lights switching on or off, chairs shifting position, windows closing or opening, doors opening or closing. These are all common paranormal poltergeist activity..
Sometimes these occurrences can be explained, it may be wind, it may be other natural forces or it may be also the person them selves generating this energy and not a ghost at all.. A common poltergeist sound is footsteps or clanking, usually movements of items is small, however if the ghost is trying to get your attention then it could be common items that go missing, as an example car keys being put somewhere else.
While science or study on this type of paranormal activity is low it is believed that poltergeists are simply upset confused spirits trying to communicate.. If you notice these sort of activity in your house it is best to try to sit down and talk to them, try to let them know it is time to pass on.. And that you acknowledged there signs..( They need to know this).. If you want, ask them questions which they can answer by sounds or movements in your house..
Poltergeists are Humans Remember..
I think the most important aspect is to try not to fear them, as they are where we are all going in someway in the end.. Try to understand them more like you would a confused human, or a kid upset.. They may not know they are dead and therefore may be confused about passing on..
The most common confrontation with witnesses and poltergeists is the understanding that many feel like you are in there house or property and are trying to get you out.. If this is the case it means the spirit is unaware that they have passed on and then think you are the ghosts / trespassers in a way.. Try to understand from there side as well.. In the end poltergeists are humans as well..