[jeargefef]

Intuition plays a big part in it. Sometimes reading a post or pm I'll get a good feeling or energy sensation, and 'mark' it in my mind for further notice, i.e. to see a pattern. For example, there used to be a theme (more than a poster) that would give me specific energy sensations when I read about it, and there has been a specific poster (that no longer posts here) that used to give me the willies everytime I read anything he wrote. (Not recently, so don't try to guess.) So pay attention how you feel when you are communicating with someone, it's not necessarily about the words, more like about the feelings you get when you read them.
And it doesn't hurt to shield.