I've had a few odd experiences - but I don't believe in ghosts or the supernatural. I think our minds are great at playing tricks on us, or interpreting natural things in this way.
When I was a child I opened my eyes in the middle of the night and saw a red devils face hovering over me. Was terrified of the dark for years. Had to sleep with a small blanket over my head to 'hide' me. I realise now of course that I'd just woken, it was dark, something was happening physically in my eyes in the same way that if you shut your eyes very hard then open them you get visual disturbances. I get visual disturbances when my eyes are tired. It was just a weird red blobby shape my mind turned into that.
I had a primary school camp in screaming hysterics all night after I saw a something. (sorry teachers and parents). When I was about 9, with an overactive imagination, and had been scared recently by the Carry on Screaming film.
About 10 years ago I was alone in the house and clear as anything heard someone shout my name in my ear. I found out this is not an uncommon form of auditory hallucination and can be caused by stress, too much caffeine etc.
My family has a photo of a 'ghost' we all laugh about. It's a very obvious man's face with beard, rather like a cavalier, appearing in a family photo. It appears where there is some clear plastic sheeting. It's got to be just a weird effect of plastic folds and light and shadow. But it looks perfect.
Other people might believe these things are supernatural. I don't. So I am very skeptical of those who believe they have seen ghosts etc. Probably similar circumstances. If you want it to be a ghost, it is, to you. If you don't want it to be a ghost, it isn't.