Since there is no definitive proof of the paranormal, it makes it hard to tell if one's house may be haunted or not. However, if strange occurrences happen on a regular basis, one idea is to start a journal and record all what you think is 'strange' and going on. Write down what the occurrences may be, times they take place, any changes within the area things occur, ( i.e. cold spots, visible anomalies, etc. ), try to take pictures, something may show up in them to help determine if you may have a problem, ( or not ) weather conditions, tape recordings for strange sounds, video recordings, etc.
You can also write down any information you can get about the place you live in, area, history, and anything that may have occurred there that is NOT of paranormal origin which may be the root of your problems - and those that may be. We also have to keep in mind that some hauntings are like a "photograph" of an occurrence of the past, which plays over and over - like a recording and not an actual "live" haunting.
Sometimes sounds like the water heater, wooden houses expanding/contracting, weather changes, etc. can cause all sorts of sounds that may seem spooky, but are all perfectly normal things and can often be mistaken for paranormal phenomena. ( Fluffy the cat jumping on the furniture, chasing a rat, it's tail or it's own shadow can do just this ). The human imagination has plenty to do with this, we often see or hear things that aren't what we think they may be, a nightmare, scary book, movie, story, can all help to influence your imagination even further.
The journal will help you determine whether or not an actual paranormal occurrence is taking place, through your notes.
If it comes to be that you are really sure that a paranormal occurrence is happening, find some experienced ghost hunters in your area, ( children shouldn't do anything without their parents consent ), who can help you out with your situation.
Show them your notes, ( what-when-how-where ), explain to them in detail what the occurrences are, your religious beliefs, things you, ( or your friends/family members), may have done to cause the haunting, ( summoning spirits through the Ouija board for example ), if you have done anything, ( prayer, house blessed, sea-salts, holy water, holy oils, etc. ), to try and stop the haunting, if you are sensitive or any other family member.. ( some spirits come about because they know that you can sense them ), if the problem started there, or at a previous residence, if the problems started with the previous tenants, etc. so that they can know exactly what the situation is about and help you.
Most investigators offer free services, and if an actual paranormal occurrence is present, can gather more information and possibly help you with your situation, ( depending on their services ). Don't challenge the spirit or anger it, that will not help your situation and may only cause more problems.