I used to direct an exercise called "Enter the Room" with actors as a reminder of human behavior in given locations.
"Now enter the room as though it's familiar."
Usually the actors would shift from observation mode to purpose. For instance, in the first case they slow their movement, taking in the space from side to side, top to bottom, gently planning their next steps. Yet it is apparent they are tentative.
But if the space is familiar, they can skip that "taking in" and go right to their purpose for entering, whether to get a glass of water, to remove and place their jacket, to find someone they know in a particular place - you get the picture.
Knowing that our movement and activity communicate our relationship to a space and those around us, it makes sense that our purpose, comfort and confidence all at once show up. There's nothing more telling than someone's purposeful, deliberate action. Comfort and confidence show up when we are deliberate.
Consider the difference in what you are communicating if you enter the space where you are to present a talk if you've been there before vs. if the first time you enter is 15 minutes prior to your talk.
Your level of readiness and ease of movement set the tone for what your audience can expect of you. Without these, your confidence and comfort are slow to show up.
It doesn't take much to be deliberate - it's simply about gaining familiarity in advance so our focus can be on purpose rather than discovery. Confidence comes from practice, including practice in getting to the right place, knowing who to ask for details and how to move forward. When we are deliberate we are focused, and so are those who notice.