I appreciate this is the forgotten ghost hunting techniques thread (which would include methods like sprinkling talcum powder on the floor to pick up any foot prints and/or attaching a single hair on the area of a door hinge, both to presumably rule out human fakery unless we're talking poltergeists) ..
I came up with a couple of new ones I think ... like most sceptics, I'm also a bit fed up of 'orb' videos .. some are more impressive than others but I'm largely with the "It's just dust or an insect" nearly all of the time .. so I took one of those double A battery operated fly zappers with me on the last invest I went on the ones that look like badminton rackets that you kill flies with. Using a night vision camera and suddenly spotting floating orbs on my viewfinder, I could, in theory, just raise the zapper into the stream of orbs. If it's insects, they'd be electrocuted and small visible sparks would be observable to the naked eye .. would dust even register at all? .. would paranormal orbs be repelled by the energy field? .. flow throw the charged metal mesh? .. glow brighter? .. I haven't finished these experiments yet but a few other groups expressed an interest in the idea because it's just as much about debunking 'orbs' as it is proving that they are something supernatural .. either conclusion would be great ..
During investigations, it's extremely common for devices to suddenly have flat batteries. The most likely cause for this to happen isn't paranormal but instead because we are often in cold places at night which naturally drains batteries anyway. The trope is sometimes "Our batteries have suddenly mysteriously become flat! .." .. so going with the whole, 'ghosts drain available energy' thing, I bought a dozen glow in the dark bouncy balls, wrote numbers on each one with a sharpie then charged them up with a light so we could place them where we wanted, the idea that any spirits could use the charged energy so would find them easier to toss around.
We haven't won the Nobel Prize yet but I welcome anyone reading to steal my low cost ideas.