As a student in a medical center, I often travel by hallway, tunnel, walkway, etc. Getting caught behind (or in front of) a fellow walker oblivious to hallway etiquette is one of the most frustrating parts of my day. I'm a bit utilitarian. I don't mind if someone wants to mosey - I just want them to do so in the slow lane.

First, realize that pedestrian expectations reflect traffic laws

If your country drives on the right side of the road, keep to the right. This reflects pulling over on the shoulder, slowing down for a multitude of reasons, or exiting the current route. If you want to stop and adjust the song on your iPod, you don't do it in the middle of the hall - would you stop in the middle lane to change your radio? Not that you stop in order to change your radio, but the comparison still stands.

Eating? Keep to the slow lane. No need to drift into oncoming traffic (of both the wheeled and pedestrian kind). 

You remember that jerk who swerved around you at crazy speeds while you were driving last summer? Maybe he was on his way to save a baby (benefit of the doubt). Likewise, someone might cut you off, shoulder bump you, or otherwise be rude on foot.

Imagine they're about to vomit.

Don't you feel better? Once they get in front of you, that vomit won't be on your back! This is just one more reason to keep to the right - let the pukers run through.

Second, no one cares how important you think you are

This is especially relevant in medical institutions, but certainly applies everywhere. 

You deserve to take up as much space as you want, right? Wrong.

Your conversation is just so interesting, others would be so listless without hearing it... 

The lunch break, bathroom, and elevator are all equalizers. Respect others waiting. Time is precious to everyone. At least for now, seeing as we don't have a solution to that mortality problem yet.

Third, be aware of your surroundings

Falling into manholes.

Stepping in dog poo on a sidewalk (where said poo is perfectly visible).

Knocking sticky drinks onto yourself and an unfortunate (now thirsty) bystander.

These are simple examples of what happens when you don't take in your surroundings. Let this serve as a warning.

When you here a tiny "excuse me," have the decency to look around. The source is likely already in your field of vision. And hoping to move through a space occupied by you. Now imagine this someone is about to vomit. "Excuse me" may have turned into "excueeeeeeeeeeeeeegggggggggggggghhhhhhhhhhhhhhhhhhhhhhhh"