It tends to vary from person to person. I tend to be on a closer wavelength to some people than others but for the most part I generally have a hard time deciding what to say or what kind of topics they are into. I guess I get on with more excitable personalities better than 'normal' people. Im natually very shy to begin with but common interests break the ice but with everyone else I genuinely freeze up just thinking of what to talk about.
What really doesnt help is that I have a angry, unfeminine voice by default so unless I am drunk or already in a loud place I REALLY have a hard time speaking up unless I wanna scare a few peeps.