A little manners can make awkward elevator rides a thing of the past.
Once you are on the elevator, it is important to consider personal space. It is never polite to invade someone's personal space, so please keep a respectful distance. Sometimes the elevator is crowded and space gets tight whether you like it or not. In this situation just do the best you can. When someone exits the elevator, think "re-adjust." There is no need to stand in the same place as the number of passengers decreases. Maintain a comfortable distance, and if in doubt, always err to greater space between you and the other passengers.
The Button Steward
Okay, let's say you are still on the crowded elevator, but you are stuck in front of the elevator buttons. Everyone that gets on looks at you uncomfortably and tries to squeeze their hand in front of you to push the floor they need. To avoid this awkwardness, just ask each new arrival which floor they would like and push the button for them. Don't forget the button pushing part. Passengers are almost always gracious toward this gesture and who knows, maybe you'll get some tip money out of the deal!
While riding on the elevator, avoid speaking on the cell phone. You may think the call is important, but your conversation is most likely not important to any other passengers. You're forcing everyone to become your audience, which is not polite. This is also rude to the person on the other end of the phone call as many cell phones will drop the call while on the elevator. It's a very simple process to end your call before boarding the elevator and re-initiate the call when you arrive at your destination.