^ This!Second most important thing is.... Move Less.
I ask my students what they think a good diver looks like and have a conversation about slow, deliberate movements that are efficient and body positioning to minimize effort/gas consumption. I don't think just relaxing/breathing, enjoying what one sees is emphasized enough. And when you see an eagle ray at 70 feet, don't chase off after it, as there is no way you are catching up and you are going to blow through a bunch of gas in your wasted effort.
However, if your dive guide does motion you to follow and they start kicking fast, chances are there is something interesting to see that if you don't hurry, you will miss (like the 3 dolphins playing in Belize - I just made it, making the gas expenditure worth it).