Terms that indicate "pay attention, we're getting ready to change"

I am a big fan of conversational tone (i.e., talk to the learner as if there were sitting in front of you in the classroom).  How would you transition to another topic in that setting?

Like Robert, I use "Now that we've reviewed..., let's switch gears and look at..."  If you want to continue the thought, but get into more specifics, you could use something like "let's delve into more detail (or take a closer look at)..."  I am also a fan of "let's see how this all fits together" to summarize the content you have just covered and give them the "why" of the lesson.  What's the takeaway?

A few others for consideration:

•  "When you are ready, click Next to..." - This gives the learner a feeling of control.  When they have finished processing the information, they can continue at their own pace.
• "Now that you are familiar with..., let's put it to use" or "let's see if you can..." or "let's practice what you have just learned" or "let's practice using a real work scenario" - This is good to use when you are going to move into a simulation, scenario, or assessment.

 Good luck and hope this helps a little!