What I think is really important is to show you're having a good time. Nothing kills the mood as much as a top-notch DJ that doesn't look at the crowd, doesn't jump around and doesn't show he's actually having a blast. This is a must. So many people pick up good vibes from the DJ that this is essential. I know it is hard not to get caught up in mixing because you need to concenctrate, but at least glance into the crowd with a big smile from time to time, show you enjoy what you see and have a good time.
One last advice: Practice mixing with both ears. I'm a right ear headphones, left ear master guy and when I first was forced in a setup the other way round I was about to die, I couldn't match shit, so I had to rely on like 3 minutes of beatmatching to not play out freight trains and after the gig I was sweating as I had done a marathon, felt horrible. I still haven't practiced the other way round yet, but everywhere I play out I make sure the monitors left. Not very professional but at least I can avoid another torture set