I'll admit, ghost hunting is a bit of an adrenalin rush, so sometimes we venture in like Brian from TAPS and bounce around like puppies and get all thrilled, and everything is a ghost, every noise is a sign..., but the truth is there's a real responsiblity in ghost hunting.
You only get one chance to have phenomenon occur just like it did that one time it happened.
Keeping records is vitally important. It's important to designate someone in the group to be the secretary with a good watch so he/she can time and write out things that occur, but there's also the background you need on the site to make your records helpful not only to the field of ghost hunting but for your future encounters.
I've been keeping records looking for anything that ties haunted places together, or timing of phenomenon, good nights from bad nights... Here are some things that are worth noting before you take off to a site. Keep your records and refer to them often. Eventually, you can plot and graph these things and see trends. These trends will help not only in research amongst ghost hunters but also to postulate how we might be "guaranteed" a haunt in a certain location at a certain time.
1. Take note the night of the hunt the mental situations for all participants. It's probably not embarrassing--you all know each other quite well more than likely. Are any women menstruating? Hormones could create stronger emotions and more sensitivity. Has anyone been angry, upset, worried, anxious, grieving? These mental conditions can actually have an effect on the hunt and the results.
2. In AZ, I take note of where the HoHoKam water canals ran. A map is at: http://www.waterhistory.org/histories/hohokam2/ The faint blue lines show the waterways. There's no proof they correlate, but to take note of such things and see if there are connections is to find ways to outsmart a haunting by knowing what areas have "ideal conditions."
3. Railways: Once again, no real proof that hauntings occur near railways. It could be that civilization developed around railways and so there's more likely to be hauntings there, but it's worth taking note of. In AZ you can try this site:
http://azmemory.lib.az.us/cdm4/item_viewer.php?CISOROOT=/shmmaps&CISOPTR=73&CISOBOX=1&REC=5
4. Geomagnetic fields/solar x-rays/moon phase:
http://www.showmeparanormal.net/Paranormal_Weather.html
This is worth noting. I have noted correlations between geomagnetic activity especially and solar x-rays--solar storms. I'm skeptical about moon phase only because nothing changes about the moon during its phases other than how much of it you see and because it's shown no correlation in my studies.
5. Weather conditions: http://www.weather.com/
It isn't just whether it's rainy or foggy (could give you strange photographic phenomenon from mist and moisture or dust in the wind), but because things like barometric pressure may change in haunted sites. That feeling of pressure in your head could be a coming storm, it could also be arriving activity. They sell watches with barometers and thermometers in them at sporting stores for a reasonable price. It's worth a try. Once again, it's your data over time that will show you trends.
6. History of the building/land/genealogy: http://www.azgab.org/project_registry.htm
This is an absolute must. No exceptions. You need to know what might have been on that plot of land, what the house might have been used for, if anyone had died there, et cetera. Most city registrar offices are helpful. The one listed here is for AZ.
7. State preservation office: http://azstateparks.com/SHPO/index.html
Once again, does the place have historic relevance.
8. Latitude and longitude: http://www.worldatlas.com/aatlas/imageg.htm
Plug in the address and see what the numbers are. There's no reason to think this might have a strong bearing, but there are some held beliefs that certain longitudes and latitudes are cursed. Anyone with some time and ambition should consider taking note of the addresses of the most famous haunted sites in the world and plug them onto a map and see if there's anything that can predict a haunted area.
9. Bedrock geology map of AZ http://geology.about.com/library/bl/maps/blarizonamap.htm
This one is important because it's long been held a belief that bedrock can affect the haunting situation of places built in these locations. Certain things like water/granite/limestone/quartz are believed to be conducive to hauntings. Let's see if this is true. Start taking note.
There are lots of other options I probably have missed. My main interest is in trying to prove of disprove some of the long-held beliefs about what constitutes a haunted site and perhaps help us to move forward into predicting potentially haunted sites. Once we have "ingredients" for a "haunted soup" we can begin to actually predict a haunted site and then prove it based on the criteria it has met.
Once again, happy hunting! Oh, and let me know if you've thought of other things to take into consideration for logging in your records. I'm always curious what others are looking for.