See, this is a very difficult question to answer because there is more than one kind of spirit, and each "type" has different behavioral patterns that are identified with them. For instance, one kind may leave you feeling empty and abandoned in their presence while another may attempt to frighten you by moving objects in the physical world. Of course, some spirits are not evil; there are occasions when a helpful spirit might guide you to something you need.
So, you see, your question is a very difficult one to answer. I honestly cannot give you any "signs" that prove the presence of any spirit around you. Sorry, but I hope this helps a little. :/
You would know about this later when you mature and realize this is all in your imagination and there is no 'afterlife', there is no such thing as ghosts (except at Halloween) and The only 'spirits' around are the ones in a bottle.
If you have wronged the spirit in some way while the person was living, it's likely to be the cause, or if they have come to you in a dream yelling at you(such as mine being yelled at because I blamed myself for his death). If your conflict was resolved then you more than likely woke up in almost a peaceful but apprehensive state. Regardless they would have more than likely contacted you asleep (since it's easiest for a spirit to manipulate and communicate in a dream). Hope that helps, any further questions just comment.
With me they use light or heat/cold. They turn lights on. The other day I was standing in my kitchen and all of a sudden felt heat on my hand,like someone was holding my hand. I stepped back and checked the whole area for heat(none). Sometimes it's cold. Sometimes they turn electronics on. Oh, and they move my things.