I'm not sure if the is usual or not, but in my (very limited) experiences, I seem to be much better at introductions than any other type of interaction.
With an introduction, the topic is typically about topics I know about (say what I'm working on, where I'm from and so forth). Or, if it is a second introduction (say, talking to someone a second time after a week or so), I can also easily handle it, since the topic is usually on the events of the week.
But the problem is, I really don't know what to say afterward.
When talking with an acquaintance who I suspect is also has aspergers, it's difficult since I know nothing about his area of interest (cars), and he isn't interested in mine (videogames, anime).
When talking to NTs, the whole situation gets extremely complicated, with constant context switches and a heavy focus on stories. Also, since I go to a tech school "everyone is a nerd", so some portion of the conversation is dedicated to their areas of study. I'm a graduate student, so I don't know any of the undergrads in the department, and all of the graduate students are very busy, so I don't get much of a chance to talk to them either.
Anyway, unless the conversation switches to something that I'm familiar with, I have absolutely no idea what to say. This coupled with anxiety (making me want to figure out exactly what I want to say before speaking, but I am often unable to do this before another context switch) leaves me extremely quiet most of the time.
Any advice on this?