When you are talking to someone, think about what their language, words and expressions, as well as their actions convey. What is that person trying to tell you? Are they trying to convince you of something or are they trying to convey something to you?
If a person is trying to convince you of something then it is very likely they have a motive or agenda guiding their actions. Salesmen try to convince you to buy something because they get a cut, they make money which is worth their efforts. Next time someone is trying to convince you think about what they are getting out of you believing them.
When a person is conveying information they are not generally using seductive language, inflection or tone. They are just putting info out there and allowing the receiving party to figure it out for themselves.
The kicker between these two concepts is that some people are doing both for the right reasons and it may come off as cold or completely counter to what you may believe. It becomes your responsibility to determine the merit of the content and not the way the info was presented. Not always, but sometimes this is required. Most will be very overt with their intentions, not in words but in the way they try to convince you or convey info to you.