Watching the Hill House Investigation and others, I see multiple paranormal investigative mistakes that seasoned investigators would never do.The investigators are purely armatures and because of this I consider all evidence gathered by them tainted. Here is some advice to professionalize an investigation:
1. Limit the amount of people investigating.(too many people)
2. Be quiet, yelling at each other can mask communication
3. Don't use a spirit board, especially one that is too big.
4. When documenting poltergeist activity place a camera unattended shooting the item being moved. Just saying no one was in there is not enough.
5. NEVER GO ALONE! Especially when no one knows exactly where you are and don't rely on phones for communication to team members, use a 2 way radio and/or a monitored X camera. If communication is lost go directly to member without discussion.
6. When sitting at a table using seance tactics, Sit perfectly still with fingertips on table, legs crossed at ankles and tucked under chair and stop fidgeting. Speak in low tones if you have to.
Take these rules seriously and evidence you collect will double, be taken seriously and you will be safe.