Zone Focus

Many articles discussed sharpness. Yes it's important and many may will disagree with me. 

But do you need to track the eye and spend money to purchase new cameras, "gun site" accessories? IMHO No.

Consider zone focus. 

For me with moving subjects I use Photopills DoF pill to decide will the subject be in focus.

When I'm using my 75-300mm glass wide open at f/6.7 and estimated distance of 100ft my DoF is over than 6 feet. That's enough for me to capture many subjects with acceptable sharpness. At f/8.0 DoF is 8 ft. That works for me. YMMV.

For those not M43 shooters need to consider the sensor size. Using a full frame at 600mm it would cut the DoF about half.

 DoF Simulator

PhotoPills DoF Pill

Choose your aperture

My DoF Rant

Become a better photographer

The following links from Steve Perry's Backcontry Gallery may likely help your become a better photographer. The links deal with Birds in Flight but the information is relevant to all photography

Shutter Speeds for Tack Sharp BIF  This applies to all photos that you have taken that are blurry

BIF Crash Course  Basically this applies to all motion, Wildlife, sports, etc.

Spot Metering Crash Course   Applies to all metering on your camera.

The right height 

What Shutter Speed?

It depends on the scene you want to capture.

To slow and you have blur? Maybe you want that.

Use a high shutter speed to freeze motion. What is high? 1/2000sec?

The thing is there is no one answer. You the photographer need to figure it out.

A shutter speed of 1/2000 sec didn't get the job done to freeze motion in this photo.