Oh I forgot, you can also get that chill around objects, places or people with strong magick auras because the energy can be sensed within a larger perimeter. Again, its usually when your back is to it that you get the strongest chill. Not sure why.
I never "learned" to be clairsentient nor read anything valuable on the subject. I've had it for as long as I can remember and I taught myself how it works and why through my own observations and experimentation and then compared it with those I know who are also clairsentient to discover what was the same reaction from person to person.