My early instructor used to get into the helicopter and get the flight time done ASAP without really teaching me a lot except how to fly the ship. It may have been too early for teaching SA.
My second instructor constantly asked me questions about where the wind is from, where I would go in an emergency, what we heard on the radio, where we are at right now, where the traffic is, if I keep scanning the gages, if it's a wise decision to fly the way I am flying over some obstacle etc etc. All these questions helped me to get the constant being aware programmed into my brain. If something was said on the radio, I paid attention. If we flew over wires, I checked them out and flew over the poles. If traffic was near us I thought about what they are doing and where they are going. If we approached an airport, I familiarized myself with the layout etc. If we were taxiing, I thought about my path first and looked out if there would be anybody in our way, etc etc... having him asking me all these questions thought me "situational awareness". If we were to leave an airport he also asked me how I would get out of there, and what would be my next step right now, before he made a decision on what we were really about to do and explained me why. He used that kind of smalltalk to teach me situational awareness also during times when I didn't expect it. He was a relatively new CFI, but IMHO he did a great job teaching me, compared to some older guys.
In the beginning I felt annoyed by these questions, as I was still struggling to handle the helicopter. But over time, handling the ship became second nature and I had more resources to be aware of what is going on around us, with the ship and the weather and other traffic etc.
So if you ask me, bug your students with questions related to situational awareness during the flight. Not constantly, but whenever there is a bit of time or decisions need to be made. This reminds the student early on to not only fly the ship and rely on the instructor for the rest. And it also gives you the chance to pass on some "rules of thumb" or "piloting wisdom" to your students.