How do you "deal with" socially manipulative individuals?

(In this particular question, I am addressing the issue at a "social interaction"/relationship perspective.)

I understand the fact that people usually find out more about a person after they have been exposed to them for a good amount of time, and can gauge a general sense of their "personality", and create a simplified characterization of that individual (such as "oh, in general, (s)he's pretty chill") to get a general sense of who they are.

I believe that I understand the fact that people usually make unconscious judgements about an individual upon meeting them, and I guess these judgements carry out throughout further exposure? (Correct me if I am mistaken. I mean, I guess judgements obviously change once you get to know someone more).

I am curious because sometimes, I would find it preferable to not be "taken advantage of" or manipulated by individuals who are professionals at doing so. However, at the same time, I do not want to become paranoid of mostly everyone and develop a sense of distrust with people.

I understand that the answer to this question is not really simple and definitive, and one "simple" solution is to ask other people about what they think of the individual, or to just learn about these things through experience. So would it be that to truly understand these things is to go through the crap and essentially internalize it?

So how does one develop an intuition of detecting socially manipulative individuals and become more perceptive of people (I guess in general, though this generalized question is probably asking for too much at the moment...)?

(As a side note, how does one differentiate between gossip and relatively less vehement judgements about an individual?)

(I guess I should also address the issue of my usage of "characterization" and "judgement", since I get the feeling that "judgement" appears to have a negative connotation).

(I understand this question seems relatively vague and general, but it is something that I have recently thought about, and I will probably try to develop the question more or something later on)

edit: Somewhat relevant video: http://www.youtube.com/watch?v=bw0mBlqwl7k

tl;dw: The manipulated person's attitudes and "fears" are what make him/her prone to manipulators...so I guess changing your attitude is a component to becoming less prone to manipulators...