Dealing with manipulative behaviour

Hello, this is my first post here. I have an issue that has been going round in my head and would appreciate some input. I have, as have most people, had several people in my life who use covert agressive and manipulative tactics to get what they want and control me. (lies, guilt trips, misdirection, vilification, shaming, distortion of facts, flattery, distraction, seduction ect...)It has been pointed out to me (and I agree) that I am a very trusting person and even quite reluctant to identify negative intentions in others, always thinking the best of people. I am, however, not stupid and once I understand what is happening I manage to deal with these people quite efficiently.

I am interested in avoiding these kind of relationships from the start, and it has crossed my mind that if I act suspiciously to new relationships, a manipulative person might refine their techniques and it would take even longer for me to identify this type of person, leading to a waste of time.

So I have decided it might be better for me to continue entering into new relationships in a trusting and slightly 'naive' way, thus encouraging potential manipulators to put their cards on the table from the start. However, what I am worried about is that maybe this kind of attitude might encourage people to act in a manipulative and covertly agressive way who might otherwise not do so.

any thoughts on this would be greatly appreciated, also I would be interested to hear about any experiences people have had or techniques people use in dealing with these kind of people.