I can honestly say that I don't sense much of anything. On one or two occasions out of my entire life, I think I may have seen something - that isn't much to go on.
But I'm led to believe that the spirit realm is like a room with a veil or curtain over it. The spirits can pass through that curtain, to varying degrees, to inhabit the same realm as we. They are not the "same," though; they are not of body or substance. But they can do it.
They sometimes don't even know they are doing it, as if they have a selective or blocked awareness.They appear to simply be going on about their "business," often the same things they did in life.
At other times they are aware of their own presence, and attempt to interact with us.
And on rare occasions it is BOTH - they are doing their ghostly "thing" AND they are aware of us at the same time.
Location has only a partial influence over this. Some places are haunted for no good reason we can determine, and those places we feel should be overrun with spirits are barren.The place a spirit haunts may be as random as they just passing through, or very specific to them and their previous life.
Flatly put, there appears to be a "set of rules," as another has said, that we are not privy to from our side of the curtain.