Most pneumonia is due to either a virus, a bacteria, or a chlamydial organism. All are more or less contagious.

It's possible to inhale a mucus droplet from a sick person who just coughed or sneezed; it can carry enough germs to make you sick. Often, though, the infection is spread by germs that a sick person leaves on surfaces in the environment. If a person with pneumonia coughs and gets some phlegm on his hand and then touches a doorknob, and you come along after him and touch it, you've now got his germs on your hand.

If you then touch the corner of your eye, or lick your finger before turning a page, or open and unwrap a piece of chewing gum and eat it, you've just put those germs into your system. If you don't wash your hands after touching "public objects" and before touching your face or food, you've essentially licked everything you've touched since the last time you washed.

It's now possible to by clear alcohol gel in squirt dispensers -- Purrell is one brand I've seen. Keep a bottle handy and use it often: it'll kill germs and help keep you healthy. This is especially important if you're working with the public or with little kids; two great sources for germs.