I don't believe in ghosts, or at least am sceptical. However the following two things happened to me.
A long time ago in the late 70s my boyfriend and I were standing on the pavement at the edge of a common waiting for a bus. He was standing directly behind me to shield me from the cold. A man walking his dog came along the path on the common, and I turned my head to look at him.
When I turned back I saw a white, kind of smokey, shape drift out of the common and across the road and up into the attic window of an old house facing the common. It was sort of shapless and almost see-through, but vaguely human shape.
My boyfriend said to me, 'did you see that?' 'yes'. 'Then say nothing about it til we get home. I'll explain then'.
We got back and he took out a notebook and two pens, gave me a page and a pen and told me to draw what I'd seen, while he did the same.
We then showed each other the drawings and they were identical, but we'd not discussed what we'd seen to make sure there was no influence.
That was a bit long, so I'll put the other incident separately.