I'm very introverted. A lot of people on here talk about how you can get them to talk on a subject they know about or really like, but I never do, even on those kinds of topics. The only time I'm ever talkative is in print. * smiles * And even then I cut it short. 
So...perspective from an extreme. 

 I also watch people a lot, so this is not just drawn from personal experience. 
A big difference between being shy and being introverted, I think, is that shy people avoid the outside world (even while they are in it), while introverts who are not shy merely refrain from adding huge amounts to it. When I am being shy, I avoid groups where there is much talking going on, I avoid eye-contact, and I generally act more nervous when someone addresses me. When I am not being shy, I engage through body language, watch and listen visibly, and answer questions to the best of my ability. (Yes, someone can switch between being shy and not being shy. 

)
Another thing about introvert conversation, which comes out particularly when there are two introverts talking or most of the people in the conversation are introverts or an introvert is dominating the conversation, is that the proportion of thought to words is much greater. A conversation I wrote recently in which an introvert was talking to someone (not a conversation where someone was talking to an introvert – big difference 

) had a pattern something like this: Two people hug each other; person asks question; introvert doesn't answer; silence, silence, silence; introvert says a sentence of four words that is not directly relevant to the question; other person says two sentences; silence, silence, silence; introvert says another sentence of four words; other person answers in one or two sentences, and they take each other's hands; silence, silence; other person begins to ask a question that goes on and sort of peters off; introvert says no; introvert answers first question of all, indirectly; other person is happy and dances; other person asks a question; introvert answers with three words. End of conversation. 
That brought to mind another thing that you might keep in mind about introvert conversation. If you ask a question of an introvert they might answer you, or they might not, or they might put you of, but sometimes they will either directly or indirectly answer the question later in the conversation. They've had time to think about it by then. 
When an introvert is forced to talk small talk (obviously he's been forced, he'd never do it on purpose 

), sometimes when he will say 'yes', or nod, or say 'right', or so on, it will mean something different from someone else. Rather than agreement, these signs are acknowledgement. Acknowledgement of the other person's opinion – acknowledgement that they just said something – so on. Example:
Me and Person are passing each other while walking across the room.
Person: 'Desserts are the best part of a meal.'
Me: Yes. * smile * <translation: I realize that desserts and other sweet things are often the favored food of normal people, especially people in your particular demographic.>
If I said anything but 'yes', in my typical introvert fashion, it would be extremely awkward. 
Person: 'Desserts are the best part of a meal.' 
Me: * stands and looks at floor while cogitating what has been said * * Person grows increasingly worried over the period of the next four seconds * Actually, though it's perfectly alright for you to like desserts best, I don't like them all that much, especially not in very large quantities. Those ones do look nice though. I hope you enjoy them. * exit *
Person: 
 
 They prefer it when you just say 'yes', or give a pleasant and non-committal grunt, or something like that. * grins * 'Yes' means assent, which is often agreement, but not always. I use it in the 'not always' way quite often. 
One introvert I know takes the initial period of three seconds that a lot of introverts need before replying and fills it with assenting with you – nodding, m-hm-ing, etc. – whether or not he is about to flatly contradict you. 

 When I saw something he wrote once, awhile after I had become acquainted with him, the effect was comparatively stark without all the instinctual agreeing. 
I have also noticed that many introverts are rather extreme when they do speak. Because they take the extra time to decide exactly what they want to say, their innate personality comes out in a different, often stronger way than it does with extroverts. If an introvert is opinionated, he phrases his words in a more opinionated way. If he is unsure of himself, his words are littered with restrictive and modifying phrases. I do that a lot. * wry * I rarely (there I go again! I was going to say never, but amended it) ever state something in an absolute manner. That's not because I'm an introvert – it's because of other aspects of my personality and philosophy. However I do it more than I would if I was an extrovert, because I take the time to craft what I say according to that personality and philosophy. See what I mean?
The reason for this long post is that I am an introvert with an interest in psychology. 

 I could keep talking, but I think I'll stop now....