Your main goal must ultimately lie with something global, or at least big picture. If you are really T subtype, maybe not. But otherwise, as an INTj, your focus is on the big picture.
The difficulty here is that..... we're not great around new people and situations. But at the same time, like it or not, our ideals and goals and visions will deal with people, and the human side of things. So there is a great deal of reservation. Even today, in a situation where everything was theoretically there -- I went to a club meeting that involved issues such as global unity and cross cultural harmony -- I was still incredibly reserved, and was completely reliant on my ego block, and more so my leading function. When asked to supply a fun fact about myself, it was a logically good attempt, but it was so laden with that it was a little odd. But the point here is that we must not be discouraged.
We, as INTjs, must still get out and interact with others, but just expect it to be a slow process at first. We work from a point and spread out, so finding that point might take a while, but be patient. And once you've got it, keep going. If it's something worth the time, then it's worth the patience and persitence, too.
It might even be very, very beneficial to interact with people as much as possible (within reason for your INTj needs), so that you can consistently update your paradigms on how to interact with others, and also, so that you can gauge your thoughts with reality. I usually build up an intense reservation when going out, especially going to a new club setting where it is blatantly obvious that I am new and don't know anyone. But you can develop courage and self confidence by going through with it anyway. I recommend INTjs to get involved with anything they are intersted in, especially if it has to deal with leadrship or big picture stuff or global issues, etc. Don't let your reservedness get in the way of the contributions you could make.
PS: and if at all possible, try to go to a meeting for the first time with someone else. I think it's a lot easier to look completely stand-off-ish or just like "I don't care and I don't want to be here, either", if you are alone. That is what happened to me today, part of the time. But being around someone I knew made it much easier. Again, don't let that threshold intimidate you -- getting on the other side, and becoming more than a very distant aquaintence can allow for more relaxation, and more influence, too.
PPS: another recommendation -- find something to do. I really dislike random socializing, still, even though I know it's good for me, etc. So ask the people in charge if they need anything to be done, or whatever. Sitting around is boring enough as it is, but through work or a job, you might be more comforatable, and it will also grant you much easier converstaion material, then having to generate 'smalltalk' from your own self. Because, as everyone should know, unless we are in a good mood, INTjs just don't care. ...so, remember --- doing stuff might be a better option than just sitting around.