These are general guidelines that should be followed for every investigation.  Each group may do things a bit differently, but as a rule, all should follow the same path to the end.  Following are some of the things we consistently do to ensure a good investigation.

Try to get some type of history on your location.  Every piece of knowledge you take to an investigation will aid you while there. 

Wear comfortable clothing.  Take into account weather conditions, and make sure you have comfortable shoes.  It is possible you will be there for hours, and don't want any distractions. Include bug spray if your location is outdoors.  Gnats are a major distraction.

Make sure you have enough extra batteries for your equipment.  Ghosts like to drain energy, and your recorders and cameras will be of no use to you without extra power.

Don't trespass.  Most cemeteries are closed at night, and many small country churches are also.  Watch for signs, or even closed circuit cameras.  Even though there may be no signs posted, use your best judgement.  Stay safe, and be prepared to verify your identity if need be. 

When you arrive at your location, try to get a walkthrough with your client, if possible.  You and your team want to know the hot spots of the location, and also specifics about how many ghosts, or any other things paranormal are happening.  If there is no client, then do a thorough walkaround, to get a feel for the place.  Notice ground holes, or low lying branches, or broken headstones in a cemetery at night.

Upon arrival, log in your time, and coordinate with the team.  All investigtors should be aware of key times and events.  Log the time that you turn on any piece of recording equipment.  Give yourself every opportunity to capture an entity, and also to hopefully verify that with other recording equipment.

Work in teams of no less than two.  You always want someone to verify your findings on the spot.  If we can't as a team feel legitimate about the event, no one else will either.  You will also feel and be much safer with a team member.

Use trigger items on investigations.  If you get a report of a child, take a ball with you, or a doll, or a childs toy.  If you get a report of a soldier, use period music, or take a cannonball, or a coin, even a uniform button.  I have had a child roll a ball over a foot, and a soldier sing along to music, even say "thank you" when I told him I would play some more.  You never know what will move the spirit to communicate.

Take as many photographs as possible.  You never know what will be captured.  And don't get so stunned by a photo that you miss something else that might be occurring.  A voice may speak, actual contact may occur, stay focused, and concentrate.  

Listen intently for the spirits to speak.  If you hear them at all, or a random voice, they are speaking to get your attention.  I recommend sound amplifiers, and even the less expensive ones they sell at any retail store work well.  When you hear a ghost speak to you or say your name, as I have, you will understand that they are still people that want to communicate.  You may be the ONE person that can hear them, or the ONE that they choose to speak to. Understand that they are lost, or don't know they are even dead.  None of us knows why ghosts are here.  Just do your best to listen for them, and to them if you are lucky, so you can help them.

Share every feeling with a team member, to see if your instinct is genuine.  You always want verification.  Again, remember if we can't even convince our own team that evidence is genuine, no one else will believe it either. 

Never wear perfumes or colognes to an investigation.  And use unscented deodorant if possible.  I have been on sites where I have smelled food, perfumes, cigars,  burning smoke, floral smells,  all manner of scents.  And follow these scents, because at times they will lead you to an event.  The moment you smell something, start watching all of your instruments.  Scents are a very good indicator of presence.  It is up to us as investigators to draw the ghost to us, or follow it to the ghost.

If you find yourself in the presence of a ghost, or spirit, try to slow your breathing, and relax.  If they don't run from you, or you from them, they want to communicate.  Words alone may startle you, but will rarely lead to anything more frightening.  Give the spirit time to speak, and don't ask so many questions that you cannot hear the voices for your own.  Many times investigators will say if they only could have stopped talking they could have heard the ghost speak.  A ghost is STILL a person, when you listen to them, they will talk.

Take multiple shots of the same specific areas.  By doing this, you may get a photo of a roaming cloud, or presence.  It is not uncommon to take over a thousand photographs and only get about twenty or thirty that show anything paranormal.  Do not get discouraged by this.  You are taking photos of  nothing that you can see, so keep taking them.  The one photo you get that will amaze you just may amaze everyone else.

When you review your voice recordings,  isolate yourself, and use headphones that cover the entire ear.  For some reason, ghost voices are usually heard as a whisper.

These are but a few of the tips that can help you on an investigation.  Please feel free to let me know of your favorite tips in the Forum.  I would appreciate the input.