There are many different theories about why a graveyard might be a good place to hunt for ghosts. Among them is the theory that the spirits of the dead may be attracted to their former bodies. Others say the body is the gateway to the other side, and those who have died use their bodies to travel back to this plane of existence. But regardless of just why graveyards are so commonly reported as haunted, there are several things you should and should not do while you're among the dead on a ghost hunt.
First is the most commonly reported don't. Ghost hunters in the media have started getting a bad reputation as trespassing when they are not allowed to be in a graveyard. Familiarize yourself with the area before you visit it, and be sure to secure permission if you're unsure of whether you're allowed there after a certain hour. Daytime hunts are preferable, but if you manage to secure permission to be there at night, be sure to get it in writing.
Next, make sure everyone you bring along is someone you know. And make sure you know they won't be causing any problems or destroying any property. Several perfectly legitimate ghost hunts have been ruined as one member -for reasons not always understood- begins vandalizing the area. Make sure you don't bring anyone along for whom this might be a risk.
And if you are hunting in the area at night, you will want to visit during the day as well. This allows you both to familiarize yourself with the surrounding area, and keep an eye out for interesting places you might want to visit. Take some EVPs and let the ghosts know when you'll be back.
And graveyards are one of the most interesting places to record for EVP. There have been several incidents where the investigators will enter a graveyard expecting to make contact with one type of spirit only to leave after making contact with something they had never expected. You should not be surprised if you make contact with someone or something that doesn't exactly match the headstones in your area. Often in older graveyards there are unmarked graves and older headstones that have been weathered by time to be illegible. However, sometimes these names are on record by the owners of the place.
And of course perhaps the most important thing about investigating a graveyard is also one of the most common sense suggestions to anyone who has seen their share of horror movies. Don't split up. If you do split up, try to make the groups no smaller than three people a piece. Additional witnesses in any area not only lend to the credibility of anyone who is visiting, but also more sets of eyes and ears are more likely to pick up on something unusual in an area.
Above all else, be safe, be respectful to those who have passed on, and good hunting!