During the Hunt:
After arriving to an area I want to search, I always ask spirits that are present for their participation and that they do not follow us from this location and to remain here, I remind them that we're not here to be bothersome or to disturb anything or anyone, upon departure I thank the spirits for their time. I know this may sound kind of silly, but they were once people too, it takes only seconds to say and could be the difference between something following you home or not.
With that said, always show respect to those that dwell there. Don't taunt or instigate the ghosts as this would, I assume, not go over well with the spirits and the rest of your group.
If you smoke, try not to do so at the location out of respect for the rest of your group if there are any non-smokers, and for whatever lurks. Some spirits may not have smoked in life and still don't like it after death. If you absolutely must smoke, go off the site.
Often times ghosts can alter your mood and cause intense feelings of dread, sadness, loneliness, depression, happiness, euphoria, etc... it's probably in your best interest to abandon a location if you're suddenly filled with dread and terror, as this could be a warning sign from the spirit world to leave. Don't be afraid to snap a few pictures or ask a few questions first.
If you're in a few groups, have some kind of equipment to communicate with one another in the case of an emergency or to alert them of something paranormal. You don't want to have to scream back and forth to one another. When eating food, be sure to respect the site and to pick up any litter that's yours.
Rule out any possibly of things that can be explained through science or common-sense. Don't just assume everything you've heard, seen or felt is paranormal. Heard a door open or close? check for a source of wind. You get the picture here.
Try not to use any foul-language, as many places of supernatural-activity include churches. Those that once inhabited these churches in life frowned upon foul-language and more than likely do as well in death. I understand being startled sometimes and you may slip up, but try to be as professional as possible.
Take lots of video, snap lots of pictures and record a lot for signs of EVP.
Ask lots of questions, and expect but don't demand answers, try to talk to the spirits as you would a human; Try not to be too repetitive though. How do you feel when someone asks the same question over and over and over, lose interest, right?
Be professional, don't vandalize the site that you're occupying. I've seen this countless times and it frustrates me to no end. Respect the home of the spirits that dwell here. how would you feel if someone destroyed your home? Be professional with your questions, don't ask if the dead like corn-dogs for the sake of getting a few laughs out of your team. They may have liked corn-dogs but they could be angered that aren't able to eat them anymore.
Don't whisper, this could confuse you when going over recordings designated to capture EVP. Always speak loud and clear.
Departure and After the Hunt:
Remember to thank the spirit-world for their participation and for their time. Again, pick up any litter you may have laying around.
Be prepared to go through lots of pictures, film and EVP recordings(assuming you took a lot). This could take many hours but must be done. Don't skip over any portion of your evidence, that skipped portion could have been where major(or minor) paranormal-activity happened. This is a given, but be sure the rest of your group knows you're leaving or ready to leave.
It may be easier to have some of the members go over certain portions of the evidence...give Member A the duty of going through the ghost-video, Member B the duty of going through film, and so forth. This will save a lot of time.
After the evidence is looked over, have all members get together to discuss the findings(if any). Try to dispute the evidence through science, if it can't be recreated then you've witnessed something of paranormal, supernatural nature. Congratulations!