The inestimable Duncan Davidson, photographer laureate of the O'Reilly tech conferences, has distilled his experiences watching thousands of speakers on thousands of stages into a pithy, useful article about how to be a better speaker. I know I need help with the last one (try not to look bored on panels — basically, my "I'm thinking hard about this" face is pretty close to my "I'm not paying attention" face).
If you find yourself walking _backwards_, you are probably pacing very vigourously. Stop. Breathe. There were a couple of speakers that were pacing so hard they didn't even bother to turn around. They just reversed direction and backpedaled. That's a sure sign you just are feeling like you have to move too much. This can also be dangerous. Stages have edges. You don't want to go off the edge of one.
If you don't make eye contact with your audience, you make it that much harder for the to connect to your message. You want your audience to connect with what you are saying, right? Then make them feel like you are addressing them. Obviously, there are many people in the audience and you can't look at all of them at once. The good news is that you don't have to. If you pick a few people in various places of the audience and lock eye contact with them, everyone else around them will feel that. It works. If it helps, you can lock eyes with friendly people that you know in the audience. Don't have any friends out there? You can make some talking to a few people before you go up on stage. Then, when you make eye contact with them, you are making eye contact with the audience and connecting with them.