Why do I bug with people I meet for the first time?

This is pretty common situation for younger people. The only way you can change this is by widening or broadening your areas of interest, you can extend your love of guitar to other areas of music, so that when you are in a different social setting you can talk more about music, talk about guitar history, facts figures, different types of guitars. But it has to go the other way too, so for example if someone has an interest in something not related to guitars you can ask them similar questions about their topic, so for example ask them what the major influences are in their topic of interest. It is also about just making up random stuff too, it's about 'how you say something' Not what you say. Just be enthusiastic about the other person. But still be honest, so if you don't 'like' the other person don't go out of your way.