Winning with consistency

For the vast majority of the tennis-playing population, consistency is the best way to win. Only at the higher levels of tennis does a flashier playing style prevail over consistent tennis with much frequency. For your flash to beat your opponent's consistency, you must hit shots hard enough and/or precisely enough that your opponent either can't get to them or can't get a clean hit on them, and you must make such shots more often than you miss them. This takes more skill than most players have. At the average recreational or club level, you can beat a flashy player simply by giving him enough chances to miss. He might hit a screaming winner now and then, but if you keep getting the ball back, his errors will tip the balance in your favor.
At the beginner level, just getting the ball back in the court, anywhere, is enough to win. Your beginner opponent won't be able to punish your short balls efficiently.
Once you reach the intermediate level, you need to start concentrating on keeping your shots deep. As long as your opponent is hitting from behind her baseline, you have an excellent chance of getting anything she hits, because even her hardest shots won't travel the 78 feet from baseline to baseline faster than you can run to them. If you hit her a short ball, it's a different story. If her shot comes from less far away, she won't have to hit nearly as hard to rob you of your time, and she'll also be able to hit sharper angles. Consistency's most essential partner is depth.
The safest way to get depth is to hit fairly high, which, of course, has the rather useful added benefit of making sure you clear the net. Even the flattest, hardest hitters should try to clear the net by at least three feet on their average baseline shots, which will mean that many will end up one foot above the net. If you can generate strong topspin, you can hit full-powered shots as high as six feet above the net. For less spin-proficient players, flat, slower shots ranging in height up through the lob category can produce depth that many opponents will find extremely difficult to beat. Back in the Moon Ball era, a number of highly ranked pros relied heavily on these semi-lobs, although the best of the Moonballers used more of a topspin than a flat semi-lob.

You might be thinking, "But, what if she attacks the net? It won't matter how deep my ball would have been if she picks it off in the air." This brings in the next most important skill you'll need: direction. If you're competing at the intermediate level, you'll only need a modest ability to aim your shots in order to foil your opponent's attempts at attacking the net. Proficiency at the net is rare among intermediates.
Of course, the ability to control direction is useful well beyond just passing an opponent who's at the net. You want to be able to run your opponent, pick on his weaker side, and wrong-foot him, but as a consistency player, placement isn't just an offensive tool. It's also essential defense.
The best example of defensive placement is hitting crosscourt when you're in trouble. You'll be hitting over the middle of the net, which is 36" high, instead of the 42" at the sidelines. The court is longer, too: 85.5 feet diagonally as opposed to 78 feet down the line. In baseline rallies, you want to be somewhat diagonally opposite your opponent's position. Making him hit from diagonally opposite you puts you close to the best position to be ready for the next shot.
If you want to win with consistency, be ready to run. You're basically trying to wear opponents down, which won't work too well if you wear out first.
Also practice your lob. It will save you over and over again, both when your opponent attacks at net and when you need time to recover your position after retrieving a particularly wide ball.
Lastly, develop a tenacious mindset. Your basic strategy is to let your opponent make too many mistakes. You're the bulldog, or the tortoise racing the hare, or whatever other critter makes you feel like you're simply unshakeable. Let your opponent glory in his spectacular shot -- then drive himself nuts missing the next five! Enjoy it all with a sense of calm, determined confidence.