Panning is an extremly challenging photographic skill. Successful panning starts with camera settings, but the real challenge is getting the physical motion of the camera right to catch the action. Throw in a bit of luck and experience to raise the bar. 

I went to my first rodeo in Gaines, Michigan a week or so ago. The opening ceremony included a series of horse and riders carrying flags from the various armed forces as a tribute to those that have served. After I shot the first static image, those riders made me think that with the right background, panning would make an interesting shot,. Unfortunately, most of the rodeo arena was surrounded by RVs, tents, and horse trailers. Not the best backgrounds. What I really wanted for a background was to get the crowd behind the rider.

I set my camera to my typical panning shot of 1/10th of a second, lowest ISO (50 on my Sony A7r3) and smallest aperture (f18 on my Sony 70-300mm lens). 1/10th of a second opens the camera to a lot of light, so my aperture and ISO had to allow the least amount of light to compensate. Depending on how bright the day is, you may have to use an ND filter to reduce the amount of light. I'd suggest to use a 3-stop ND filter when panning, then raising the ISO or lowering the aperture to compensate.

With the settings complete, and knowing my preferred background, I only needed to focus on my physical technique. Panning requires a smooth motion, level to the ground. Ideally, your subject is moving along a line that is parallel to your camera's sensor. Not toward or away from you. A subject moving toward or away becomes larger or smaller, changing it's relative size as it moves, causing blurring. 

For panning, set your highest frame rate (motor drive from the film days). I use the mechanical shutter, not the electronic shutter, to eliminate the possibility of 'rolling shutter' image errors.

When panning, your body is the tripod. Just as you lock your camera to the tripod, you need to lock your support of the camera with your body. Hold the camera by supporting the lens underneath with the left hand while actuating the shutter with the right. Elbows should be pulled in tight to your torso and the camera should be pressed up against your nose and face. This reinforced grip reduces extraneous motion. Your body should be oriented square to the path of the subject's motion. You don't want to be twisted up tightly as you pan. Turn toward the subject. Start shooting. Follow the subject as you rotate your waist through legs in a smooth motion. Keep shooting as the subject passes through that ideal location directly in front of you moving parallel to the sensor plane. 

It will take lots of tries. There are a ton of variables. For example, with this horse and rider, they are moving across the frame, but also bouncing up and down, causing blurring. And the flag just flutters. More blur. But that blur also shows action and movement.

Each pass, you check your images. If you're just not getting close to being sharp, shorten the shutter until you are (1/20th, 1/30th of a second or faster). But remember, the images don't have to be perfectly sharp, just acceptably sharp. 

Keep trying. Keep practicing. Practice on bicycles, busses, cars, joggers, boats, whatever, until you get the hang of it. If you want more background blur, you lengthen your shutter for more challenge.