Well look at me, offering advice on the same day I signed up. But Psychology is my area, and I believe I can offer some advice on remodelling, by no means am I a PUA, but I have done social remodelling on myself, now I just need to sort my "game" out.
The important thing is analysing yourself, being able to look at your unconscious behaviours and becoming aware of them. Like for instance since you say you're being quiet around people, a good place to start is when someone is talking or recalling anecdotes etc. simple things like nodding and saying "yeah" occasionally and laughing when everyone else does makes you look involved. That's just a basic thing to get you started.
But the key thing is, it's vital you get rid of this image in your head, if you're always expecting to be labelled as the withdrawn quiet guy, you will constantly play up to this without being aware of it. so that's where the self awareness comes in, so you can say I'm not that guy any more, and try to begin to get more socially involved. (A great book, but very scientific is Joe Dispenza's - the science of changing your mind, or his other breaking the habit of being yourself. Both very accessible in terms of understanding how the mind works and teaching self awareness.
Next a simple trick to get people to like you is asking questions about them, it's well known in psychology that people remember you as a nice person if you ask them questions about themselves. Then if you can share an experience of the same thing great. Also like game I would say, have some prepared stuff to talk about with people, you've got great openers from just talking about the work or lecture you've just had. But also if you really struggling to connect with people, right down a list of your hobbies and interests, like books, films, TV, music, and slowly drop those subjects in there to ask about, build some common ground.
A major thing I noticed in growing up, that everything is taken a face value in early to late teens, I'm only 22 but I have realised that people of that age range will categorise you no matter what on how long you hair is, the label on jacket, whether your clothes are too baggy or skinny. The funny thing is that's how groups get divided, and these groups claim to be so individual, cool, and original by frankly looking and acting exactly like each other. By suppressing exactly what makes them individual inside by allowing themselves to fit in. Make sure you don't do that, don't pretend to be someone you're not, pretend to be the idealized version of yourself and set about plans and manageable ways of doing that.
Also just so you are aware, change is hard, what you're essentially doing is a mental refurbishment. The brain hates that, the brain loves patterns and balance of the same things, this is why people give up on so much like PUA, weight loss, smoking, any thing and everything that takes time and effort.
One last tip, be open to new experiences that's the best thing you can do, do new things as much as you can, learning, new experiences, that will keep you occupied and inspired I believe, don't sit around dwelling and wishing, make it happen, it will be hard and it will take work, and it will take time, don't expect it to kick in tomorrow.