As I've been studying the qualities that come together to make an ideal spirit vessel, I have come to some conclusions (and a lifetime of encounters) to say how these things can come to be more readily.
If you want to up your chances of having a ghostly encounters, these are my tips:
Geomagnetic storms: First and most simple way to have a much higher chance of encounters. Do solar flares (which cause geomagnetic storms upon the earth) cause haunting activity or simply make it easier to perceive? Perceive, I believe. Humans can have agitation of preexisting mental issues and extremely vivid dreams during geomagnetic storms, so something within our own brain's wiring allows perceptions we don't normally possess. Check out solar weather and proceed accordingly. I have found electron flux is particularly correlated with active research nights.
Geology: Yes, granite, quartz, limestone, copper seem to be at higher incidence in areas that hold a haunting well. Why is this? Piezo electricity might be at work and other factors. Just see that granite is associated with radon gas, which might in some way affect our perceptions, once again.
History/construction: A building with clutter, darkness, twists and turns can have much captured within. In terms of feng shui, positive energy likes open pathways and light, bad energy likes things such as clutter, darkness, cul-du-sacs and graveyards nearby. The kind of history a building possesses is critical too. The Amityville home's history might be tantalizing, but it would appear that no one suffered long and agonizingly, they died without even realizing what was about to happen. You take a sanitarium or sanitorium and you have a location that might have repeated, lengthy torment and pain that create a kind of staining of the building itself.
Once you pass the above location choices, we move on to what you can do while inside the building to capture an encounter.
Movement: Here's the fact - you will not see a Bigfoot sitting around a campfire, hoping he comes in to check you out and you don't sit around a table and expect others to enter the room. You must wander about. Most encounters occur on foot, while going down hallways, entering rooms, basically startling the unsuspecting perhaps, but more likely upping your chances of being in a room that has something going on.
Intent: As insane as it sounds to not stalk spirits, it's critical in finding them that you keep your mind clear and open and not focused on hunting them down. In fact, if you can daydream a bit of innocent thoughts, you are much more likely to come upon them. There's a reason for this - focus. Like that pot that won't boil if you watch it, if you enter a building focused on expecting to see something in the dim light, you are likely to miss a sound. Even if we think we are fine driving while talking on a cell phone, that focus of our attention to a different part of the mind, ruins our other senses, it deadens them, so we don't realize the light turned red. You deaden the other senses when you focus too much attention to the visual.
Balancing speech and quiet: There is a balance in speaking and silence. It is fine to talk to another partner lightly about something funny or endearing, like bragging about your kids or some other subject that others would like to eavesdrop in on, but there need to be long pauses of speaking. Upon occasion, you get a reaction to your speech, but to pick up on any reaction, you must be silent. Allow yourself one sentence of speech, then a lengthy pause.
360 degrees of observation: Here's the thing, our ears have these fantastic "shells" that pick up sound waves, but we need to be directional to pick up the nuances, so you must be pivoting 360 degrees often for visual and for sound. There is nothing more exasperating than seeing a figure out of the corner of your eye, and turning too late. We get focused on creeping around with a flashlight like Scooby Doo gang, but the fact is, things are all around us, pivot often!
Your emotional content: I have found over the years that your emotional content that very day seems to affect your electrical energy/chemical energy, and you can be a repellent or an attractant. There seems to be a correlation of seeing spirits during times of depression or blues, hearing them during times of anxiety and fear, and having objects move when angered. When you are emotion neutral, you are at the mercy of other elements including how psychically in-sync you are that day. We all have PSI skills and it's crucial in discerning spirit activity. If you are not a person who seems himself/herself as intuitive, you need to develop that sense because it is the one that lets you know ahead of time; goosebumps, feelings of being watched, oppressive heaviness on the sinuses of your face.... I suggest you work those skills often by doing online PSI testing regularly to get used to the in sync feeling of mind and body when you get a right answer. That is a sense you can learn to remain in for longer periods of time. People who frequently meditate also understand this ego neutral position that allows input of "other" info.
Repeated exposure: It goes without saying that, if you have not had a ghostly encounter, you have likely not been frequently exposed to locations that have activity. The more often you are in one, the better, and the longer, as well. Weekend hunters are not going to run into anything except happenstance, but those who stay in a place for a week or more, are likely to run into repeated activity. The best advice is to stay at a haunted B&B for a vacation or take up a friend in an offer to stay in their ancient cabin in the mountains. Whenever you can be in a place for a time and let the place get used to you, you experience what those who live in activity haunted homes experience. When I was growing up, we could go weeks without much of anything and then a burst of activity. When people moved in or moved out, more activity during that breaking in period. Investigators have much going against them including that their very energy is new to the building. The longer you hunker down, the more it relaxes and shows itself.
Semi-darkness/evening: It's not magical that ghosts only come out at night, it is to our advantage, though, to search then. Less traffic, less noise, and a semi-darkness makes our eyes better able to discern things moving, shadows, contrasts, and with less background noise, subtle sounds can be heard.
Props and the like: Can an object be haunted? Not in the way we think. It's as if everywhere we have been, everything we have handled is tagged with us, a tracer. The soul, not being limited by the 3-dimensional physicality, can be in all the places it has ever been (at least to our limited 3-dimensional way of thinking). Playing music for the times might create ambiance, but does a spirit have auditory canals? Perhaps not, but vibrations can be attractive. Rhythmic tapping for a time and then silence, rumbling and then silence, running a fan and then silence, they can all trigger a reaction, as many investigators have found with Tesla coils and Jacob's ladders and the like. Electrical, vibratory, harmonic - all potential attractants for the disturbance of the very atmosphere (not necessarily because ghosts need it to materialize). A good example is we humans with auditory canals, music can create so many emotional feelings within us, deja vu, anger, excitement, utter soul-numbing peace, and all by the vibrations being processed into our mind, but those sound waves can also affect our body, such as is the case with extreme bass sounds that resonate through our chest when someone has loud bass speakers playing.
You can up your chances of having para-encounters, but it doesn't happen if you don't place yourself out there, and often!