We are lake divers in my neck of the woods, so we stress control and staying off the bottom. Obviously, this does take a little time for some divers to master. Overall, I think our divers are good about staying off the bottom because we dive in silt.
That being said, I agree that as an instructor I probably do not spend enough time explaining the importance of not bothering ocean life. While we tell our students "take only pictures and leave only bubbles". I think that we spend most of our time with the mechanics of diving and safety.
Hindsight being 20/20, I think we do most of our conservation preaching in conversation as opposed to making it a larger part of the course. We do stress this when we do dive trips to the ocean; but, you are correct, we need to spend more time on this early on in the Open Water stage.
Thank you for this forum topic as it has shown me something I can improve upon as an instructor.
To the other instructors reading this, make an honest assessment of your own instruction and ask yourself if you have been doing your share as a leader in the dive industry. I can honestly say that, in the past, I have not.
As far as giving tips to new divers... none of us would be old divers if the old ones before us did not tell us the proper way to do things.