I think I have only once physically seen a possible ghost. I was staying in a house on a remote northern island for a week's work experience (I was living in the rooms above, while the practice was underneath). I had been told that emergency services sometimes stayed in the house too, but that it would be empty for the duration of my stay there.
Well, one evening, I came back from a walk, in through the front door, down the hall, and came to enter the living room, when I caught sight of a man in blue dungarees sitting in a chair nearest the door. Well, not expecting anyone to be there, I immediately turned tail and snuck back towards the bedroom, then thought, hang on a minute. If there was someone in the house, I had best introduce myself, and would rather know who they were, given that I was living there on my own. So I turned round again and went back towards the living room. Only to find there was no body there!
This left me rather confused and shaken. I swear blind there was a solidly built man in orange jumper and blue dungarees sat in the living room. However, a did a skirt of the entre room, and kitchen, and every single room in the little house, but apart from myself, it was totally empty! Needless to say, I locked all the doors on going to bed that night, and kept my mobile phone pretty handy.
Other than that, I sometimes have a feeling of uneasiness in some properties I have lived in, and I remember one in particular, where I just Had to recite prayers out loud whenever I was alone in the house. In my current house, I kept getting a rendition of a song called Hey, Jude in my head whenever I went near my room after purchasing a second-hand bed. In the end, I got fed up and despite feeling a bit of a mad woman, had an out-loud one-sided conversation telling whoever was tied to that bed and singing the song, that the bed was no longer wherever it had come from, that it was mine now, that I did not much care for Hey, Jude and would rather have other tunes in my head, and that basically this was my room, and to kindly go away lol. I don't know if it was a placebo effect, but apart from the odd occasion, I have my own songs now.