My wife is a very well educated person when it comes to etiquette.  She’s read the Emily Post books, and her mom and grandmother have taught her a lot about how to act in certain situations.  Something her grandmother taught her comes up often when we’re talking about what to do in a certain situation.  Her grandmother’s advice is simply this:

“Do what brings the least amount of attention to yourself.”

For instance, if you are at a dinner party and drop a fork on the floor, don’t pick it up.  Picking it up calls unwanted and unnecessary attention to your mistake.  If you’re trying to decide what to wear, aim on the side of overdressed – people won’t notice that near as much as the other way around.

This lesson can help us build better interfaces as well.  When you’re thinking through interactions on a page, or how something should respond to a user, remember – do what calls the least amount of attention to the interface.  Or, said another way, take the least disruptive route.

For example, what should happen if a user makes an error on a form?  A modal window causes disruption and calls unnecessary attention to the mistake.  A subtle (but noticeable) Ajax error message to the side of the form quietly nudges the user to correct their error.  It’s less disruptive, and simply put, more polite.

Reducing this disruption can also be thought of in another light.  As someone uses your interface – be it a website, web application, kiosk, touchscreen, mobile device, whatever – bring the least amount of attention to the fact that the user is using a piece of software as possible.  Remember, your user doesn’t care that they’re using your software, they simply want to complete their task enroute to their ultimate goal (which probably doesn’t involve using your technology all day).  To that end, focus heavily on keeping the implementation details and visibility out of the consumers mind.  Error messages like “Wrong data format” are an example of doing this incorrectly!

So, as you’re designing interfaces, remember my wife’s grandmother’s advice – do whatever brings the least amount of attention to the fact your user is using a piece of software. It’s just good etiquette.