Well, I don’t see how you can know a person’s intentions, so how can you be fooled by them? People might say what their intentions are, but without any indication of the reliability of their statements, you can’t make an estimate of your confidence in what they say.
You might try Neuro-linguistic programming. I’m not sure if I’ve understood it very well, but it seems to me it is about observing people’s behavior, and making some guesses about the subjective experiences that lead to that behavior, and then using communication skills to improve the outcomes of your interaction.
If behavior and stated intentions don’t match, that’s a great sign that a person is not very good at predicting their own behavior, or that they are out and out lying. If you pay attention to behavior, you can probably make better predictions about what they will do then they can. Just don’t tell them you’re doing that. People hate being told that they are lying to you or lying to themselves.
Ah, belay that, me hearty. Sometimes it is helpful to tell people about the dissonance between their stated intentions and their behavior. It takes a deft tough, however, to know when to talk about it and when to leave it alone.