Be heard..be seen
Okay, so you've got this band together and it's going really well. Good players and tightening up nicely. The only problem is that the audience doesn't seem to respond the way you expect they would if you're getting as good as you think you are. So what's wrong? What's still missing? Well, if you're like most bands in this predicament, you may be forgetting that music is a form of communication. A more sophisticated version of the spoken word, because of its ability to convey emotion with sound. Communication involves not only words and sound but also physiology. You've probably spent a great deal of energy on tone and rhythm, but what are you doing onstage while you play? Are you doing anything to involve people in the show or are you hiding comfortably by your amp?
If you want your audience to watch you, you have to do something VISUAL. I've seen too many otherwise good bands that just play to each other or stare at their guitar necks. It's probably the same way they play at rehearsal and they don't even realize it. I believe the goal of the show is to get the attention of an entire room focused on one thing. The song. More accurately, each and every movement of the song, as it unfolds. It's almost like mass hypnotism. It's very powerful and equally hard to pull off, but people will remember the show because they were in it, not just at it. They may not even be aware of why they enjoyed your band so much but they'll come back. To work the room or hold the crowd is an art, but there are some simple things you can do to get better response quickly. The rest can be considered ongoing experimentation.
Number one is, get into a band you like! Life's too short to play shitty tunes with jerks.
Second, be ready in every way. If you're not comfortable with the material, you can't expect to play with confidence and blow away your audience. If you're late, or your equipment sucks, you're going to be distracted. Frustration is probably not what you want to send out to the crowd.
Next, be aware of what is happening OFF the stage. See what the audience likes and what they don't like. Look at them, make eye contact, let them know you are performing for them. I'm not saying you have to jump around like an idiot (unless of course, you feel like one at that moment). Just move around, do something. It's a live performance. BE ALIVE.
Remember that it's important to be real. You love music or you wouldn't be up there. The only thing worse than a good band that's boring is a crap band that thinks they're the hottest thing going. You can tell they're just doing what they're supposed to do because no one would be that far removed from reality (would they?) Above all, open up and let go. Get off on the music. The audience will get off on you and then feed the energy back. Everyone plays better in front of a responsive crowd. It's what we're there for. The band's job is to make the audience feel the way the song feels to them, to express emotion through the performance and start the cycle. To get "caught up in it" whether it's a sad ballad or a no brainer party tune.
You're supposed to be able to do just as good a show for the three people who bothered to show up on a Tuesday night as you do for a packed house on Friday. I know that's an idealistic goal but you have to at least try. If you're not at least a little uncomfortable you're probably not doing enough. if you go far out of that comfort zone, you'll appear phony. You may not feel right going mental in an empty house but if you don't do something, the room will stay empty. So learn to read your audience and give the people what they want.