The first way to tell whether you are serving correctly is whether the ball is going where you want it to go. I know that sounds very simplistic, but the reality of things is that proper mechanics tends to result in high levels of accuracy. If you are consistently hitting your target then chances are pretty good you’ve got things right. That said, chances are you’re reading this article because you aren’t as accurate or powerful a server as you’d like, so let me provide you with some checkpoints you can use to get yourself on track.
Are you finishing your serve balanced? If not, there’s something wrong. Usually, it comes down to your toss. If you toss the ball too far to the left or right you’ll end up leaning in that direction to try to make proper ball contact. Either that or you’ll be serving the ball in that direction when you didn’t intend to do so. If you find your weight well onto your front toes, then you’ve tossed the ball too far forward, while having to arch your back and lean backwards means a toss behind your ideal contact point. All of this can be fixed by improving your toss.
Is the ball spinning when you want it to float, or floating when you want it to spin? That is a function of your ball contact. You need to make sure you’re stricking the right part of the ball in the correct way to get the desired effect.
Is the ball coming landing short or going too far? Distance in serving is all about the speed of your hand at contact. Swing your arm faster to hit the ball farther (notice I didn’t say swing harder). Swing your arm slower to hit the ball shorter. Make sure to keep your ball contact firm, though. No floppy wrist or mushy hand!
Does your shoulder hurt when you serve? If so, it probably means your arm swing is off in some fashion – assuming you don’t simply have an injury from something else, of course. This again could be related to ball toss, but it could also be a function of your mechanics. This might be hard to judge by yourself, though. You’ll likely want the help of a coach in evaluating your arm swing – or at least the use of video.
Which brings up perhaps the best way to gauge whether you are serving properly. Video yourself serving and compare it to video of someone who serves properly. There are many tools out there these days that allow for side-by-side analysis. This will let you see how your technique stacks up against the good server in the areas of body posture, arm preparation, toss, footwork, and follow-through.