How do I 'read the room' and adjust my pace while lecturing? I am a PhD student. I've never taught a lecture-style course before. I just filled in for my advisor at the last minute, giving a lecture in an undergrad course.
I taught from the lecture slides that my advisor had prepared, drawing diagrams and examples on the whiteboard where I thought it was warranted. I stopped often and asked if anyone had questions, and if nobody did I posed questions to them, e.g., &quot;What do you think is the benefit of this system over that?&quot; &quot;What did you learn about X?&quot;
My impression was that approximately 30% of the class was pretty engaged, asking and answering questions, etc., 50% were taking notes and paying attention but not really speaking up, and the rest were zoned out. I think this is normal (from what I remember from being an undergrad), so I thought I was doing OK.
However, towards the end of the lecture, a few students said that I was going much faster than normal. And, I did get through more slides than my advisor said I should expect to, so they're probably right.
My question is:

What clues do you look for to &quot;read a room&quot; to tell that you're going too fast, even though people seem to still be &quot;getting it&quot;?
What can you do to slow down, beyond asking if anybody has questions and bringing up more examples (I can only think of so many examples)?

I am asking specifically about teaching undergrads, because I think they are more difficult to read than postgrads, or senior academics in the audience of a conference talk.  But I would appreciate answers that apply to the latter scenario as well.
Also, I understand that things like clickers and discussion groups can make a difference, but I am asking specifically how to improve my lecturing, not how to restructure classes so I spend less time lecturing.
A related question is How to improve myself as a lecturer, where one answer says &quot;Never assume that students follow you&quot; and suggests you &quot;see if they get the idea, sort of get the idea, or don't get it at all.&quot; I tried to do this, and it seemed like the students that were willing to engage were &quot;getting it.&quot; Apparently they were getting it, but I was still going at a speed that made their heads hurt :)
In my experience it's easy to be misled by a few good students who are able to engage with you and answer your questions. This doesn't mean the majority of students feel the same way of course. I always try and bear in mind the weakest (and often the quietest) students in the class and try and not be lured into accelerating due to a few bright sparks at the front.

Asking if there are any questions or bring up examples is a good way to try and gauge the classes response. But if the class is shy or unresponsive (as is often the case initially) I find it very hard to know whether I'm boring the pants of them or they're completely lost.

A simple trick is to give a short relatively straightforward exercise and ask everyone to do it there and then. It should only take a minute or two. You can then briefly walk through the students and ask them how they are getting on. It should become obvious if many of them are struggling. Walking among the students and directly interacting with them isn't going to suit everyone though and if the class is large (or the seating is inaccessible) it will be more difficult. But it's crucial to get some feedback and if that means taking a more proactive approach then why not? I make sure to smile and encourage them since some students will be nervous if the lecturer asks how they're doing.