This was an excellent question posed by Julie and a few other readers and friends.
Do you ever feel like there are people around you and fear overwhelms you? Like you have to run away and hide from it? That sinking feeling you're being watched or told to get out?
Well first off, there must be mention of mental disorders, as I do not want to reinforce mental illness by saying it's ALWAYS ghosts. Paranoia, Schizophrenia, Anxiety Disorder, and a host of other challenges can cause this feeling - so if you suffer from any mental illness, take that into consideration first. There may not be any ghosts around you, but your brain is making you think that. Brains are double edged swords sometimes, so to speak.
Next, I believe we all have a varying extent of psychic ability. Just like people have varying extents of sensory ability - like I can see more colours than some people can see, or smell things that most people can - but I can't see that far and I have overly sensitive hearing (I can hear less but more loudly). Some people have 20/20 or better vision, and others need special glasses just to see a little bit.
You might be psychic and not know it, and your brain is telling you there are spirits around, or something bad or important is going to happen, or happening. Recently I felt sad, grieving anxious, and fearful for no reason, and then my friend called me with a death in the family. Perhaps when you get that feeling - someone in your circle of loved ones is sick or in trouble. When you feel really horrible fear/panic and you have no history of mental illness, you might want to call your friends and family to see how they're doing. Don't tell them you have a bad feeling unless you have some kind of specifics - even a vague sense of what's wrong.. like "Don't get into your car till tomorrow" or "don't walk home tonight, get a cab" or "go visit the doctor, and get him to check out your lungs".
You might be sensing spirits, and they can vaguely sense or observe that you are sensing them.. and they might be frustrated that you can't hear them.
You may be feeling a message from a spirit but you're unable to decipher it due to lack of practice or fine tuning your skills.
You may be in the presence of a malevolent spirit, in which case just get out of the room or area. If you have no choice, like if it's at work or home or school, keep thinking or saying (depending on if there are people watching) "please leave me alone" or "I can't understand you."
(I'll add more to this later)
This weblog documents my experience as someone who communicates with the dead. I will share as much as possible without revealing the person or people that commissioned me to speak with their loved one or loved ones.