Once the trainees have been asked questions about the last logical lesson, (and correctly answered them), the instructor should state what the aim of the next lesson is. It should be made positive by implying that the trainees will have no trouble with it:
"At the end of this lesson you will be able to etc etc......." The alternative is, "Now this is really difficult and we need to get this right". Unsurprisingly that doesn't go down very well!
This early part of the lesson should also contain an introduction which provides the trainees with a good incentive to want to learn. Statements such as "You don't want to damage your employer's product/racking/forklift do you?" or "people have been killed by a forklift tipping over......." are designed to get the trainees to take the lesson seriously so that they want to learn.