Lookout lookout lookout they hammered into me on FIC course. Making a good lookout before you enter a manoeuvre and teaching the student to do the same is the easy part. The hard part is maintaining the lookout whilst the student attempts said manoeuvre and you monitoring and guiding them.
A few weeks ago I nearly busted the LTMA because I was paying too much attention to getting the student to sort out the speed in a climb and failed to notice he had wanded from the heading I had given him. A good lesson learnt for me there.
I am still an inexperienced FI but I try to tell myself if you're not doing or saying anything LOOKOUT and then look for the nearest suitable field in the event of an engine failure.