Ghost hunters on TV usually just annoy spirits into paying attention to them, but I'd argue the most convincing ghost footage comes from people who weren't expecting to capture paranormal activity on film.
Check out this footage captured by a couple living outside of Bradford, Pennsylvania, for example. They were just trying to make a video to send to their family members in California, but after a few seconds, they realized that something bizarre was afoot.video-player-present
It's interesting that the guy with the camera actually saw the ghost as he was filming. People don't usually notice these things until they watch the footage over again.