BEFORE YOU GO:
Safety first. Never go to a location alone, even if you are familiar with the place. Always use the buddy system. This is for two reasons: one being safety and the other is if something paranormal happens you will have a witness to verify it. Otherwise it's just another story. Always bring a cell phone and a first aid kit. Some places you may want to investigate might not have power or are in disrepair. Wandering around in the dark in dangerous conditions is a recipe for somebody getting seriously hurt. Also, in some large abandoned buildings it's not the dead you have to worry about, but the living. These places provide plenty of hiding places for unsavory people who might not be too happy that you're there. There is a certain TV show where the cast brags they get locked in. This attempt at bravado is promoting unsafe situations and is just plain stupid. They claim it is to decrease the chance of contaminating their investigation. Following sound protocols can reduce contamination. Besides, if there is someone already hiding out in the building, or there is animal activity it really doesn't matter if they're locked in, now does it?
Always get permission, whether the property seems to be in use or not. An old cemetery or an abandoned warehouse is really enticing for ghost hunters. But going there without permission is still trespassing and illegal. Getting busted not only creates a mark on your record, but it reflects badly on the paranormal community. Plus, it can be dangerous because there are not-so-nice people who also like to use such areas for drug deals, prostitution and other illegal activities who won't like you intruding.
Even if you get permission, always carry your ID. If a police patrol shows up, they will likely ask you to present it. If you don't have it with you, there could be issues that you don't want to deal with. Telling them, "I'm with XYZ Ghost Hunters" isn't going to cut it.
Even though there are no "professional" ghost hunters, because you are dealing with the public, you should act in a professional manner. Wearing tee-shirts with nifty team logos doesn't necessarily make you "professional". When you're dealing with clients, be respectful to them, as well as their property and each other. Put egos and any internal disagreements aside. Do not make claims you cannot back up. You cannot prove, nor "certify" a place is haunted. You might be able to present evidence that something paranormal is going on, but that is it. It is very irresponsible to claim you can "cleanse" a place from ghosts or energy. There is no proof at all this is possible and you may make things worse for a client. Finally, don't claim you can "help" a ghost. Again, there is no proof that anyone can, and claiming such is nothing more than an ego trip. Plus, if there are spirits around, it is quite disrespectful to make promises you can't keep.
Be aware there there are emotionally and mentally unbalanced people out there. If a client seems too eager for you to prove they have a ghost, acts like they are "on something" or if the situation just doesn't feel right, walk away. Unfortunately, there are cases where attention-hungry clients deliberately manufacture evidence or some clients are outright delusional.
Common sense tops the list. If you are the type to get freaked out over every bump or squeak you hear, you might want to find another hobby. Remember, the vast majority of claims have natural causes. So if you hear banging in a building it is likely due to wind, animals, or vibrations than it is ghosts. Be aware of weather conditions and your surroundings. If you hear "whispering" and it's either windy or raining out, it's very likely you're not hearing a ghost. Be aware of conditions that cause drafts and remember air is not static, it is in constant motion. So even if you're not standing directly in front of an open window, air currents can gust past you. Doesn't mean it's a ghost.
Bring a notebook and pencil. If you experience something that seems anomalous, write down the time and location so you can cross reference it with your audio or video, or find out what other team members where doing at that time. I remember one investigation where we were asking if anyone was there, could they knock for us. Then we heard knocking! But guess what? We found out other investigators were on the floor above us doing "shave and a haircut" knocks at that time.
Flashlights are important. In a separate post I will discuss in more detail why I am not a fan of investigating in total darkness. It really isn't necessary and there is physiological evidence that doing so makes you more prone to visual misperceptions. Again, there may be locations without power, so getting around and investigating safely requires flashlights. Also, in EVP sessions, it's good to know where everyone is and see if they shift or move you can "tag it" so you don't misinterpret that sound in review.
Voice recorders might be the favorite tool of paranormal researchers. If you are really serious about getting into paranormal investigating, spend your money here. Buying cheaper, low-end recorders is a waste of time and money. I will go into more detail about recorders in a separate post, but you must know is that low-end recorders produce false-positives because of poor frequency response and low sample rates. So ambient noises can sound like words or phrases. Also, low-end recorders do not have good shielding against radio frequencies, so your ghost might really be a radio broadcast.
Every ghost hunting show I've seen has investigators using EMF detectors. I go will into more detail about EMF detectors in another post. EMF detectors detect electromagnetic fields and fluctuations in those fields, that's all. They do not detect ghosts. A good and cheap EMF meter to detect natural EMFs is a compass. Again, if you want a "real" EMF meter, save your money and pay for a higher-end one. KIIs, which are really flashy and therefore make great TV, are useless for investigating. They are unreliable because they also pick up radio frequencies from cell phones, wifi, CBs, bluetooth, etc, and it is impossible to differentiate between EMFs and RFs with the KII meter. Don't waste your money one on (like I did a few years back). Learn how to use your EMF meter as well as what environmental factors can affect it before you bring it on an investigation.
Bring a bubble level. You can get these at any hardware store. Many times you might hear claims where people feel like disoriented or even like they are being pushed by unseen hands. Uneven floors and stairs can create this effect. Add complete darkness, which also creates a sense of disorientation, and suddenly you have reports of a mean ghost that pushes people. I don't think it's a coincidence that old buildings have reps for being haunted, since it's common with them to find high EMFs and uneven floors.
Bring masking tape and trigger objects. If there are claims where things move on their own, bring a trigger object, like a toy, candy, cards, (whatever might be relevant to the claims or history) and some masking tape. Place the object and tape a square around it. If the object moves out of the square, you might have some paranormal activity going on. But for the love of all that is good and decent, do NOT use a ball as a trigger object. Vibrations, air gusts, gravity (uneven floors) can easily make a ball move, so it's not the most convincing evidence.
Cameras. If you're just starting out, any camera will do. Actually, if you're not just starting out any camera will do. There is a lot of buzz about full-spectrum, and infrared cameras. These are neat, but useless if you don't have a control shot from a regular camera to use as cross reference. Again, learn how your camera works. Learn about low light conditions, and various exposures and how they cause light streaks, shadows, "see-through" images, etc.
Bring extra batteries for your equipment. Make sure you fully charge rechargeable batteries and use fresh batteries each time. There is a theory about entities draining batteries. Sometimes it's only colder temperatures that do this, so just be prepared.
Investigations are a waste of your time if you don't follow some basic protocols in order to eliminate false positives and misidentification. Throughout the investigation, especially during EVP sessions, there should be no whispering. Simply talk at a normal volume. When doing EVP sessions, set your recorder down or on a tripod. This eliminates false positives from you brushing a finger against it or it against your clothes. Start every session by stating the location, the time and who is present. Verbally "tag" every sound, like people shifting, moving their feet, coughs, burps, stomach growls, etc. Save pictures for before or after an EVP session, as you should try to remain as still and quiet as possible.
When taking pictures, try to take "control shots" when you first enter an area. Since you will likely be in low or no light, say "flash" before you take the picture. That way you don't blind your team mates and reduce the chance of them taking a picture with your flash reflecting off of something and causing a false positive. Cut off the camera strap, and tie long hair back to avoid "vortexes" showing up in your photos. Also, be mindful of temperature. If it's cold enough to see your breath you can discount any weird ectoplasm or mists that show up in your pictures. Hold your breath when taking pictures, and be aware that mist from breath can show up as long as 30 seconds later. And absolutely no smoking allowed. If you have smokers on your team, designate specific break times and areas for them to smoke.
Taking shifts. If you have more than two people, you might consider splitting up to best utilize your time. Be sure to position the two or more teams far away from each other as to control noise or light contamination. If you're investigating for 4-6 hours (or more), take into consideration time to unload, set-up, and doing an initial sweep before hand and then time after to pack up. It's a good idea to have a check list so you don't leave any equipment behind.
Plan breaks. Bring food to snack on during the breaks (not while investigating). It will be distracting for you and others if your tummy keeps growling during EVP sessions.
This is obvious, but do not drink alcohol or take drugs before or during the investigation.
Provocation: just don't. A lot of TV shows use this for dramatic purposes. First off, there is no way to positively ID a ghost. So if there is no way of knowing if you're cussing out an evil pirate or someone's innocent grandma. Plus with provocation, if there is a negative entity around it might cause more problems for the clients after you leave. If you want to increase the chance of activity or interaction, use trigger objects as discussed before or maybe even play period music, if feasible.
When in doubt get out. Some people don't believe in negative entities, and that's fine because there is no proof they exist. However, there is no proof they don't exist, either. If one can accept the possibility of ghosts, I can't understand why they would dismiss the possibility of other non-corporeal entities. Personally, I like to err on the side of caution. If you think there may be something negative, walk away. Do not confront, or threaten, or provoke. This may look cool on TV, but if these things do exist, then you could be opening yourself up to a dangerous situation that isn't easily resolved. Better safe than sorry. Refer the client to their clergy in such cases.
Finally, remember you will need a lot of patience for investigating. Be prepared for long nights where absolutely nothing interesting happens. Be prepared to review a lot of video and audio where you catch nothing anomalous, and then most anomalies will have mundane explanations. Those who claim to get a lot of evidence frequently are either misidentifying false positives or are being dishonest. But being patient and overly analytical with your evidence has a payoff: when you do get that rare catch, it will be much more likely to be authentic and therefore harder to debunk.