I have this theory that all you need to know about communication is talk to everyone like they are young child. Speaking slowly, loudly, clearly and with good eye contact is the best thing you can do. No one is ever going to say, “You are being TOO clear.” That will never happen.
I got this theory by working at a summer camp last summer. I realized that when I spoke to the kids I was forced to be very concise because of their attention span. Once the fall came, it was my first time being a TA. I quickly realized that when I spoke to my students I also needed to speak slowly and concisely. Do this and you will reduce class confusion.
Another thing I learned working at a summer camp is when you speak slowly it makes you appear much more confident and in control. For the students, it gives them a sense of security. If you look or sound flustered it is more likely they will not trust you or, worse, not listen to or respect you.
Tell the children/students EXACTLY what to do. Don’t give them options. In my experience a lot of the time freshman are confused and nervous about everything. For them, if they ask what they should do about a situation, I tell them exactly what to do. For older students, I feel it is okay to give some options but in general if you can just be concise and tell them exactly how to do something, chances are they will respond better.