Unlimited Options for Andre
The awe-inspiring baseliner of the 90s has been Andre Agassi, whose prodidgious talent and unrestricted shotmaking makes for something to behold. His tennis is impressive for two reasons:  first, heís always in the best position to strike the ball, and second, there is literally no shot he canít hit with confidence.
   Most every baseliner is limited in their choice of shots. Some can only hit winners from the perimeter of the court, and then only to one side; others are dangerous when hitting forehands from the center of the court, but relatively harmless from the sidelines. Agassi, however, has virtually no limitations; he can hit winners from anywhere to anywhere. Plus he can move in on balls hit with topspin and hit them on the rise, sometimes even surprising himself (I think) when he hits them crosscourt with such hard angle that nobody can get to them. In my way of thinking, he sets a standard that every serious baseliner can measure himself against.

Drives and Angles
It helps to understand how the ball's ef-fect assists in producing shots that are difficult to return. The crosscourt drive is effective when the ball lands deep and/or bounces high, forcing the opponent to back up. The key is to make the ball rise after it crosses the net. The stroke is low-to-high and the ball's flight is low-to-high. Topspin and depth are a tough combination to handle. (Maintaining depth with heavy topspin is problematic; moderate topspin or flat shots make it easier.)
   Sharp angled shots contradicts theories of percentage tennis (the mar-gin-for-error is smaller) but the effort pays dividends down the road. Angles open up the court, maneuvering the opponent out of position so one can attack (usually down-the-line). Plus they're a good defense against the net rusher.

On-the-Rise
To produce a low-to-high, high-bounc-ing ball, it helps to play the ball on the descent. 
Getting in position is the hard part -- the stroke is relatively easy.  Once you've executed the shot you must anticipate the short ball -- by moving up.
   The idea is to make the opponent back up to play your shot, then, when he returns short, to move up and play the ball early in its bounce, so he has less time to react. You're literally stealing time from him -- time to pro-duce his stroke and time to get in posi-tion.  Tennis players are time bandits.

Change Grips
Two handers who change grips are more likely to develop an all-court game.
 A Continental grip on the backhand has several advantages:  it enables the player to handle both low and high-bouncing balls; it facilitates topspin and underspin; and it makes it easier to volley well.

Before the Ball Bounces
Preparation is a prerequisite to execu-tion -- it ensures contact in front.
   Three things take place before the ball bounces in front of you: (1) Draw the racquet back with the non-dominant hand, turning your shoulders, looking over your front shoulder; (2) Close the racquet face by laying your wrist back, to facilitate topspin; and (3) Move your feet so you're in position to make a solid shot.
   In practicing the timing of the stroke use the four-count system:  back on one, hold on two, strike on three, recover on four.

Practice Your Timing
A well-hit ball has a distinctive sound and feel; keying into it provides direc-tion in gaining more effect in your shotmaking.
   The ingredient most necessary is re-laxation.  Arm and hand are loose on the back and forward swing, tightened at impact, relaxed again on followthrough. Timing can be practiced with a bucket of balls: Prepare the racquet, toss the ball up and in front, then make contact before it bounces. Concentrate on the timing of relax, squeeze, relax. Properly executed, it's the racquet head, not your arm, that creates  energy. Pace is natural.

Use Your Free Hand
The non-dominant (free) hand serves a useful purpose.  By holding the racquet before and after strokes the player can relax his hand and change grips.
   During a long point tension builds and shots fall short; gripping the rac-quet tightly  reduces your chances of hitting a power-ful shot. Releasing the grip is a key fundamental.

Keep Moving
The tennis master makes it look easy -- like every shot is hit off a batting tee. Watch his feet and you'll notice they move continually. 
   Because the ball bounces funny (and sometimes we miscalculate), it helps to keep those feet moving after the ball bounces in front of you.  You search for the point of contact as much with your feet as with your racquet. 

Don't Look Up
Among the many unnatural (call them acquired) skills in tennis is keeping the head steady throughout the stroke. The temptation is to look up to watch where the ball is headed. Looking up lifts your head up; the resultant jerkiness spoils the stroke and undermines the shot.
   The best habit is to momentarily watch the spot where you contacted the ball, looking up as it clears the net. It'll feel unnatural at first so you'll have to work on it for a few months to get the habit.

Free and Easy
Each player's strokes are different but all good groundstrokers share one thing in common: the ball is contacted in front and away from the body so the arm swings free and easy.
   If your stroke feels cramped and un-natural it'll help to spend some time with the backboard, moving your point-of-contact away from your body and far-ther in front.

Backhand Down-the-Line
If you favor your forehand, a reliable backhand down-the-line is a big help. This shot often elicits a crosscourt return to your forehand. 
   Many players move poorly to the forehand; a deep backhand down-the-line opens up the court so you can attack their backhand.

In Trouble, Find the Middle
When the smart tennis player gets in trouble from the backcourt he generally opts for the down-the-middle return; from there the opponent has less angle with which to hurt you.
   One of the characteristics of advanced players is their ability to hit offensive shots from defensive positions; when they're pulled off the court they'll hit the ball hard down-the-line, tempting their opponent to the open court.

Pass When You Can
Better angles and lobs give you a defen-sive strategy. Instead of a desperate all-or-nothing shot, the cool response is a soft angle or a lob.  Sometimes it makes sense to play the ball right at the volleyer -- let him create the angle. When he hits short move up and go for the clean pass.

Use the Serve to Attack
Offensive backcourt tennis begins with the serve. An ever-varying combina-tion of speed, spin and placement will keep your opponent guessing and re-turning short.
   You'll develop the habit of thinking in combinations of shots. Instead of hitting a lot of second serves (and then backing up), you'll be making a first serve and looking for a short ball. 
   When you do get stuck behind the baseline keep in mind that pace is less effective than spin. A high-bouncing ball can do more damage than a hard-hit ball that doesn't pass the service line. 

Calculating, Not Impulsive
A crafty baseliner doesn't get suckered into trying impulsive plays: He does-n't get drawn into the net and he doesn't hit to the open court when he's not set up or mentally prepared to do so. His scheming way is intimidating to oppo-nents--not only does he make fewer mistakes but he gets inside their head.
   Winning long points is often a mat-ter of maintaining depth and varying the pattern of your play. Hitting five or six balls to the same side will occa-sionally elicit a dumb move from your opponent. 
   Angles are weapons. Getting the op-ponent off the court is sometimes the only ticket to the net. A reliable cross-court forehand is a great source of con-fidence.
   Attack the strength. Going into a match knowing which stroke is weaker is helpful, but you must also know how to exploit it. Don't get tricked into making mistakes because you're trying to get the ball to the weakness. You'll end up playing to half the court. Better to first go to the strength, which opens up the weakness.

Excerpted from Watch the Ball, Bend Your Knees!