Unlike most sports, running, at its core, is pretty simple. You don't need to study any rules before you can start, and it doesn't involve complicated skills like learning how to swing a bat, ice skate or throw a ball. However, while running is easy to get started, that doesn't mean you can ignore learning proper running technique and form.
Despite the fact that running is an activity most of us have done in some manner or another since we were kids, very few runners have a "perfect" natural stride. Perhaps your arms crisscross your torso instead of moving straight forward and back. Or, maybe you don't exhibit proper hip extension because you don't generate enough power from your hips and glutes. Whatever your specific form deficiency may be, your chance of injury increases dramatically unless you can gradually correct your technique flaws as you intensify your training.
The difficulty in changing form is that there is no absolute "perfect" running style you can copy. While we do know the basics of what good running form should be, how that looks for each runner will be quite different. Improving your running technique isn't about mimicking another runner's form. The "perfect" form for you is one that allows you to train injury-free month after month, year after year.
In addition, changing your running form is a difficult endeavor. The most complicated factor is that no one aspect of your running form occurs in isolation. For example, changing the position of your footstrike impacts your hip flexion, cadence, stride length and almost everything in the biomechanical chain. As such, you need to keep the entire body in mind if you plan to make changes to your form.
Despite the fact that running form is an interconnected and dynamic series of movements, breaking down the specific elements of proper biomechanics can be an effective way to teach a runner how to run more efficiently. By breaking form down into isolated, specific sections, you're able to focus on one element at a time (your hip extension for example) without confusing yourself with everything else going on in the kinetic chain (your arm swing for instance).
To that end, performing a series of running drills a few times each week can be a great way to improve your form—if not entirely from a physical or mechanical perspective, but at least to have a better cognitive awareness of what proper form should be.