Photos, audio and EMF readings, logged with time, date and location.
Experienced investigators shoot a mix of stills and video, use flash to catch mist or orb-like artefacts, and try to talk themselves out of every result before they trust it. The evidence that survives that process is the evidence worth keeping.
Etiquette: state your intentions calmly when you arrive, never taunt or provoke, and thank the space when you leave.
