I used to enjoy informing other people of why their arguments were flawed. It gave me a sense of knowing but I probably rubbed a few people up the wrong way at the same time. Now, I generally leave other's beliefs alone and say nothing that might challenge them directly. Instead I invest in sharing information that I think might expand people's models of reality. That way, they come to the information themselves instead of being influenced by an agenda.
Habits are hard to change and in terms of retraining mental pathways/changing beliefs, it seems to me that it is most effective when contrasting information from numerous and diverse sources is available. For instance, me alone telling somebody about something might not have an effect in changing that persons beliefs, but if they hear it from numerous sources, or in different contexts or from different media then it's more powerful.