The only instrument of importance is the Rotor Tach.....we live and die by Rotor RPM. During a real engine failure.....and autorotatiive landing....one cannot have too much Rotor RPM at the bottom. The Airspeed Indicator will show you Min Sink and Max Glide airpeeds (if you remember them) and when used in conjunction with Min Nr while maneuvering will give you the best performance for your particular aircraft. They are reference points.....not etched in stone.....move the controls to make the aircraft do what you need to do to hit that target you picked out at the start of the maneuver.
Arriving at a bad spot with bags of Nrand some airspeed is far better than landing at a great spot with no Nr and no airspeed. Always have something in the bag to trade!
Pick your exact spot....tree....bush...pond...road junction....or landing pad...helideck...ocean....what ever and do what is required to find yourself hitting that exact spot. If you over arc....S Turn, slow down, lower the lever some more....under arc....raise the lever a bit...get to the best glide airspeed and hold it until you regain your angle or cannot make it to the exact spot you picked at the very start of the maneuver.
Get into the habit of picking the exact spot you intend to land every time you begin an approach.....don't just aim for the airfield then pick a runway...then pick an area of the runway...then pick where on the runway....pick the exact spot.....visualize the skids setting on an exact spot....from the very start of your approach. Get into that habit during "normal operations" and you will do the same thing during an "Emergency".