Because there are no real 'ghost hunter training' courses, and people are easily influenced by the media, anyone can become a paranormal investigator and not know a single thing about proper investigative practices!
This is especially hazardous to those who are bothered emotionally by strange things happening around them, as these are the people who seek supposedly knowledgeable investigators for understanding and guidance. Once equipped with false information, a downward spiral of fear and need often follows! (Paranormal gurus are supposed to help relieve their clients of terror and misunderstanding, not elevate it.)
Good investigators are few and far between, but they are out there!
And so, I have composed a general guide of important questions to ask in order to help you find the good ones:
(If you are not 100% sure the team is right for you, keep looking!)
#1) What are ghosts?
This is probably the most important question you could ask. Anyone who can define the term 'ghost' in less than 5 sentences, or is quick to generalize them as the spirits of the once-living, are NOT the people you want.
No one knows for sure what a ghost really is, nor can we lump them all into one category. While we can detect trends and similarities, every haunting is different.
#2) What equipment do you use?
Video and still cameras, quality audio recorders, and logic are all good answers. EMF detectors (or compasses) are okay, too.
Unacceptable answers include ghost boxes, dowsing rods, phone/tablet apps, Ouija boards, and other questionable methods. If unsure, Google it and use your intelligence.
#3) Could you explain your 'scientific method'?
There are a lot of groups out there who claim to be scientifically based, but aren't. Review their collected information (pretty much everyone has a website), and make sure it is thorough and not biased. The more info, the better. You're looking for solid evidence, theories, and in-depth explanations. If they cannot provide this, they are probably not reliable.
Regardless of your personal beliefs, do not bring in a group of religious or 'spiritual' founding. These people are hardly scientists, and tend to jump to conclusions. Supposed psychics, mediums, etc. are of a different category altogether, and if that's your thing, invite them separately, afterward.
#4) Do you charge for your services?
This is an iffy subject. Most reliable teams do not charge their clients, but do accept donations in order to fund their project. (However, there are always a few exceptions to the rule.)
You see, paranormal investigation is not considered an actual science, but rather, a pseudo-science. There is no 'sure thing'. It's a matter of theorizing and testing/debunking (hence, this is why 'scientific method' is important).
And because there is no 'sure thing', and often clients harbor a lot of emotions about what they're experiencing, it seems wrong to charge for services. A paranormal investigator attempts to help, not 'cure' of 'ailments' as a doctor would. And so, if successful, a client donation is much appreciated, but not necessary.
Also keep in mind that client situations are taken on for research and understanding. An investigation is often considered a learning experience, which is also payment (of knowledge and experience) to the investigator. A 'guru' who does not recognize this probably has an ulterior motive.