I've noticed that some people who are very intelligent, and especially those who are socially intelligent, can often make people respect them even in new groups because they always find interesting and relevant things to say. I'm not that kind of person.

It's possible to take on the growth mindset here. I myself have improved in this area and I know people who have improved far more than me.

Note that only about 10% of this is what you say. The other 90% of it is the energy you bring to what you say, which mostly manifests in voice tonality, body language, facial expressions, and eye contact. All of those things in turn are influenced by your mental state and frame of mind - specifically, you want to feel present, open, interested, and calm.

All of these represent habits that you can take on 1 at a time, as long as you make sure to train them the way you would any other habit. If you're interested in pre-made training programs that go through this, here's a short list: http://lesswrong.com/lw/mdh/open_thread_jun_22_jun_28_2015/cicl