A good, quick rule of thumb in a technical training class is that your participants should be working on their first hand-on exercise within fifteen minutes of the start of the class. This will give them the “buy in” they need to feel like they are learning something.
That’s a tall order: you probably have to welcome the participants, describe the class, distribute the materials, tell them when lunch hour is, explain the location of coffeepot and restrooms, and have everyone introduce themselves, all in fifteen minutes. (At a chemical plant where I periodically teach, I am required to read aloud a lengthy list of safety instructions, too.) Try to get all of that out of the way quickly.
There’s an added bonus to quick introductions: you’re setting expectations for a rapid pace for the class, so you can cover material quickly if necessary, instead of cramming in the last two chapters at 4:45. (You can always slow a class down if needed; it’s difficult to speed one up.)
Some topics require some theory at the beginning, which can lead to a lengthy “chalk talk.” Try to find a way to do a hands-on exercise first, then cover the theory: “Here’s why we did what we did.” See if that improves class participation and satisfaction.