There are so many things that can distract a learner from focusing on content:

What happened to them before they came into the classroom
Exciting things / traffic happening outside the classroom window
Competing visuals, i.e. flip chart pages all over the walls, active slide projected on the screen, working groups milling about the room
The temperature of the room
And the list could go on and on

What's a properly prepared instructor to do? Can we adequately plan for every possible distraction before we walk into a learning environment?

We can plan for more than we think, and frankly, that's our job. Preparation solves at least 90% of the challenges we will face in the classroom. Generally speaking, we all know we can:

Know our content inside and out!
Mastery of the content means less time obsession over ourselves, and more time to focus on who really matters -- everyone who cared to show up for our class.
Review every discussion and exercise that is planned, and ensure ahead of time that they physical environment supports moving into and out of workshops quickly, and supports maximum learning in general.
If we need people in groups of 4-6, and we have tables that seat 3, classroom-style setup with 5 rows and 2 columns with an aisle down the middle, how do we give instructions to minimize confusion and get right into the activity? If panoramic windows are to everyone's left, can we draw the blinds in a way that we keep great natural light and keep the passers-by on the sidewalk from garnering attention from our learners?
Be strategic about where focus should be in the class.
If we are not talking about the slide on the screen, turn the screen off (B or W on the keyboard, or use the presentation remote). If we aren't going to use the flip charts anymore, take them off the walls, or consolidate them in the back of the room. Use a tool that keeps track of the room temperature, and aim for a comfortable range of 68-73 deg F. We know if it is trending out of that range, it's time to actively manage that, before we see too many shivering bodies or people start peeling off layers of clothing and soon no one remembers what class they're in.

Is it possible to change circumstances in each learner's world outside of the classroom, so that they are not distracted by "real life" that is happening without them, while they are in class with us? Often, the answer is no. And we have a unique opportunity to exercise a form of leadership that is so effective that what happens inside the classroom is far more important and urgent than anything begging for their attention outside the learning environment. More on that in the next post.