I'll be honest: it's a crap shoot. Unfortunately, there are a lot teams in the field who claim they are in it to help people when in reality they are in it for the "thrill" and to get attention for themselves in a "fringe" field. It takes some research on your part to find someone reliable who will help you find answers to give you some piece of mind.
AVOID TEAMS WHO:
Charge for services. This field is based on theory and speculation only. At this point, investigators are just gathering data. There is no accredited training nor certification for ghost hunting, so it is unethical to charge for an unsubstantiated opinion.
Claim they are "certified": See above. If they claim they are certified, they were either scammed or are trying to scam you. All it means is they took a seminar from someone who doesn't have any more formal credentials than you or I.
Claim they can certify a place as "haunted". No one has proven ghosts exist, let alone what they are or how they behave. There are diverse theories out there - none proven - as to what makes a haunting: spirits of the dead, residual energy, time slips, psi activity, etc. If you want a certified haunted location, go to an office supply store and make yourself a certificate. It carries the same validity.
Use psychics in investigations: In today's search engine world, there is just no way to trust any "hits" are genuine. Also, a false hit, generated from a psychic's overactive imagination, can create unfounded fear. It makes for good theatrics on TV, but if you truly want answers, skip this side show.
Post photos of orbs, streaks of light, or mists as "evidence": Any sincere investigator will have done their homework on how cameras work and what causes these common photo/video artifacts. So groups who post such are either ignorant or are trying to fool people with false evidence.
Claim they get a lot of evidence: Most seasoned investigators will tell you valid evidence, captured using strict protocols in a controlled environment, is rare. So either these groups are misidentifying false positives or they are being untruthful.
Claim they can "cleanse" a location: No one can back such claims with any proof. In fact, there are many anecdotal claims where such attempts made things worse for the client. There are only two types of people qualified to handle such cases: medical professionals or trained clergy.
Who "name drop": Just because someone met or got pictures taken with TV paranormal investigators does not make them a better investigator. (I have a few such pictures and it doesn't make me special, trust me). And with bad protocols and misidentifying obvious false positives being shown on many of the shows, it's not something I'd advertise. Also, just because a group is part of a team "family" that is profiled on TV does not guarantee anything. Such team families are huge and therefore hard to monitor and manage individual groups or members.
Who pad their "stats": Experience is important, no doubt. But it doesn't necessarily guarantee a better investigator. For example, if someone has been investigating for over a decade and they still present light streaks due from long exposure as evidence, that experience is pretty much null and void.
Other things to consider: Don't be afraid to do a background check on members or ask for a criminal screen. You want to be sure who you are inviting into your space and around your family and possessions, is trustworthy.
LOOK FOR TEAMS WHO:
Look for logical and natural explanations for claims first. We cannot identify and analyze valid paranormal experiences if we don't rule out all other explanations first. Sometimes, it's a safety issue. High EMFs and carbon monoxide levels in a home can not only cause people to have seemly paranormal experiences, but are dangerous.
Use use objective means of collecting data: Anyone can walk in and say they feel a presence or an energy. Doesn't mean it's there. But when there is other measurable data, through pictures, or audio or EMF readings to back it up, then you have something to properly analyze.
Are very selective about what they will consider and post as evidence: Quality over quantity. Who do you think could better figure out your claims? A group who has 100 dubious pictures that can be easily explained or a group with one picture that no one has been able to debunk?
Do not make unsubstantiated claims or promises: As mentioned before, this field is based solely on speculation and theory. There are no absolute facts or answers at this point, so no one can guarantee any conclusive outcome. Valid investigators collect data, offer their opinion on their findings and and advise clients with possible solutions.
Who respect your privacy and will keep your case confidential: Investigators should be more concerned about assisting their clients than their own egos.
Who tell you what to expect from them during and after the investigation: It's your space, and you are entitled to know what the process of an investigation will entail.
Who invite you to participate in the investigation: Some teams ask clients to leave the location altogether and it may be for honest reasons: to prevent noise contamination, etc. However, it is your space and you have every right to be there. A good team will teach you protocols to follow so you won't impede the investigation.
Who are happy to answer your questions: Valid teams value educating the general public about the paranormal, as well as the equipment and techniques they use for investigating.
Who are easily accessible by phone or email: This is self explanatory. If they are hard to contact, they might not be the most reliable people for your investigation.
Remember, you are the client and it's your space. If investigators show up who act unprofessional or if you feel uncomfortable with them, ask them to leave. You have more to fear from the living than the dead.