You could try observing other people; watch them, listen to them, figure out what they talk about. If you can work out how other people do it, you're one step closer to being able to do it yourself. Being naturally quiet isn't necessarily a bad thing, though. People love a good listener. All you have to do is get them talking, then really listen to what they're saying. Try to understand their point of view. Look interested. Nod occasionally. Not much else needed. Would any of this help you?
This is a problem which cannot be helped by advice, but needs personal treatment by a psychotherapist. I assume you live in a part of the world which does not provide such services routinely, so this may present difficulties. I really do not know what to suggest beyond the advice already given by Dragontongue