When it comes to hallway usability testing, the less said the better. Just grabbing the next 5 or so people you see and watching them use your product turns out to be nearly as effective as hiring a consultant. (Plus it's a lot cheaper.) Making lightweight testing more complicated robs the method of some of its value. So you might be better off skipping this article if you have a busy hallway near you.
On the other hand, if you work a goodly distance from your nearest co-worker usability testing will require a bit more work to pull off. For one thing, you'll need to schedule people across timezones and figure out how to screenshare. So you might as well use the excuse to do a slightly more sophisticated process that will result in slightly better testing.
Set a goal
Most of the time the goal can be:
Find out what confuses new users.
It's probably implicit to the very act of watching someone try out your interface for the first time. But it can also be useful to have specific things you want to find out. For instance, when we felt the Stack Overflow Documentation product was ready for public launch, we ran some usability tests with this goal:
Can new users contribute to Documentation?
Without a goal, it can be too easy to delay launch to fix problems of ever-decreasing importance. (For what it's worth, our second round of tests have been very encouraging and launch is fast approaching.)
Write a script
When you spot someone struggling to complete a simple task you know how to do, it's human nature to step in with advice. But that instinct risks breaking the very thing you are trying to understand. Minor confusion using an interface for the first time is normal and expected. But there's a huge difference between figuring something out after a few minutes and never figuring out how to use some feature of your design. You'll can't tell the difference between those types of failure if you step in and solve the problem prematurely.
So you need to play a part in strange sort of improvisational performance where the test subject is the star. Your job is to say and do as little as possible, which is where a script can help. A good script will give just enough direction for the star to push the plot forward:
Put the test subject in the mindset of a particular user.
Encourage the test subject to verbalize their thoughts while using your interface.
Place the test subject on the path at the point you want to start testing user interaction.
Provide subjects tasks you hope they will accomplish without telling the them how.
Give people a chance to reflect on the experience
You might also want to ask some questions at the end of the test. Be aware that people probably won't answer concisely if they were in the proper mindset for the test itself. On the Documentation usability test we recently finished, I asked people to give a "two sentence review". Instead, everyone rambled on with general impressions. Some of them noticed they hadn't answered the question at all, but I assured them it was fine: we weren't really looking for a back-of-the-box blurb.
If you want to focus answers on something concrete, ask binary or multiple choice questions such as:
Do you feel using the product was more intuitive or more confusing?
Having just a two options forced people to summarize the entire test into a useful data point. We did notice that this evaluation is highly variable, however. Some people who struggled rated the experience as intuative while people who seemed to pick up on the interface quickly called it confusing.
Much of the hassle of doing remote "hallway" usability tests depends on the way your organization is structured. Most people can't drop everything at a moment's notice to spend an hour learning your interface the hard way. So you'll need to schedule around other meetings, regular work hours and timezones. If you use Google Calendar, the Find a time feature can be useful.
You'll also need to pick (and test out!) some sort of video conferencing system. At a minimum, the test subject needs to share their screen. It's also useful to record the session so that everyone on the team can review the test. (I like to remind the other person we are recording and make sure they are fine with it at the beginning of the test.) We use Zoom, but Hangouts On Air or a number of other systems should work just as well.
Fix the problems and test again
I won't lie: watching usability tests is painful even for people, like me, who had nothing to do with the design. It's got to be so much worse for the developers and designers watching people struggle to use their work. But then you gotta move on and figure out what caused the problems and fix them. If you do a good job, the next test will show a different set of problems. Hopefully less serious problems, but you'll never be done finding roadblocks that users will run across.
This is where having a concrete goal helps. If you keep going until you solve all the interface problems, you'll never finish. But you can test until you meet your original goals and know that you are done.