I generally don't refer to the book unless there's a mistake or I want to emphasise something really important (eg 'make sure you know this table' or 'memorise that definition') or add something to something in the book eg add something into a diagram or graph. I basically introduce a topic in a couple of sentences and then going into harder content. I draw a lot of pictures on the board that I've planned out beforehand (haven't been using technology because it tends to waste time imo and I suck at setting up a projector/computer) and then ask people questions or to contribute in order to draw the pictures/teach the class. Get people to come up and draw/write on the board. Ask people if they understood everything --> move on to the next topic.
I am a fan of the broader overview thing. I feel like I'm going through the most important points in each of the classes, without spending much time on things that can be rote learned without much conceptual understanding (eg plant hormones). I decided to do it this way because everyone in the class is at a different level in terms of what they already know, prereading etc - by covering more things, even in less detail, you appeal to a wider proportion of the class. Otherwise some people get overly bored/don't learn anything because you spend the whole time going through something they already understand. I would prefer to go over something in less detail and ask people to approach me to talk about it if they didn't understand properly, or they want further clarification. But there's no 'right way' to teach any of this - this approach might appeal to some students and a slower more complete approach might appeal more easily to others.
I finished everything I wanted to go through today, without spending as much time on the action potential as I would have liked to, but it's okay!