When playing live, there are certain basic concepts one needs to keep in mind. One big thing is that you are there to entertain the audience, not yourself.
As part of that one you need to engage in some kind of social communication with the audience. A simple step is to actually look at the audience with your eyes, or at least avoid watching the instrument. This is especially true of laptop DJs, I do believe a large part why laptop DJs have a bad reputation – “reading email on stage” — is that they don’t try to establish an eye contact with the audience.
This is also true of musicians, watching the instrument or fretboard rather than looking out looks like one tries to avoid a connection with the audience. Yes, there are passages that are tough to play without looking at the fingers, but in general it’s a good practice to start watching the audience when you play. In general, it’s easy to separate the beginner bands from the veterans, the beginner ones are not watching straight out, rather looking down at their instruments.
Another option is to actually use verbal communication with the audience, talk to them. This is where I also think the DJ system breaks down, it’s seldom I’ve seen a DJ take a microphone and at least say: “Hi, thanks for having me here” or something similar. Instead there’s this coolness factor of hiding behind a non-microphone environment, play the records and then go home.
There’s of course no need to go to the extremes and chat the audience to death or be a lounge lizard. But taking small steps will make the connection, the audience is happy, remembers you, purchases your tracks, comes back for more live shows and so on. If you still are shy, use sunglasses as a half-way step.
If you want to learn from a pro, check out how Bono from U2 works on stage.