If you find that you are hitting your drives too low to the ground then the golf ball will not be travelling the maximum distance that could be achieved as it will be hitting the ground too early during its flight.
To maximize your tee shot distance, you need to launch the golf ball upwards and into the air because the higher you strike the golf ball, the longer it will fly in the air and the longer it is flying in the air, the more it is travelling forward and therefore the further distance you will achieve.
One of the reasons that drives can be hit too low is because you are de-lofting the club face as you strike the golf ball by closing it, or rotating it to the left (for right handed golfers). A lower amount of loft on the club face will produce a lower flighted golf shot. To correct this, work on opening the club face a little more at impact so that it is square to the target rather than rotated left. To do this, focus on your hands. If you are closing the club face and de-lofting it, your right hand is rotating over your left too early before impact. You should work on swinging the golf club through impact with your right hand slightly more palm upwards towards the sky, rather than palm downwards towards the floor and this will hold the club face more skywards and add loft to the club, producing a higher ball flight.
You may also be hitting low drives because you are striking the top of the golf ball from the lower part of the club face of your driver, rather than striking the centre of the golf ball from the upper part of the club face. If this is the case, initially check your grip pressure as holding the club too tightly pulls the club head up from the floor and the lower part of the club face will be presented to the upper part of the golf ball. Check your grip pressure. Do this by squeezing the golf club as tightly as you can and we will call this a 10. Now halve this pressure to a 5 and then relax your hands just slightly more to a 4. This is the correct pressure to hold the club at and you should find that your strike improves.
You may also be striking the upper part of the golf ball from the lower part of the club face because you are bending your left elbow through impact. If you are doing this, effectively you are shortening the distance between your shoulders and the club head and so you are pulling the club head up from the ground and the ball and you will strike the lower part of the club head into the upper part of the golf ball. Work on maintaining a straight left arm throughout your backswing and downswing to ensure your left arm is fully extended as you strike the golf ball and this will present the upper part of the club face to the centre of the golf ball and produce a higher flighted golf shot.
The club head will also be pulled up away from the ground if you increase your spine angle, or posture during your golf swing, so also work on maintaining this so that your head remains at the same height throughout your swing allowing you to return the club head correctly to the golf ball for a higher tee shot.
You will also hit low shots if you have too much weight on your left side during your golf swing with your driver. Having your weight too much on your left side, will produce a very steep angle for you to swing the golf club away from the golf ball at, during your backswing. The club head will attack back down towards the golf ball at a very steep angle and the golf ball will be launched downwards towards the ground and will be hit low.
To correct this, place slightly more weight on your right side for your tee shots and this will encourage you to make a more rounded, flatter backswing action, that allows you to swing the club head back towards the golf ball with a more sweeping action and with a shallower angle for the club head to approach the golf ball at. This promotes a higher launch and therefore, a higher golf shot.
To hit higher tee shots and achieve more length with your driver, work on these points the next time you are at the range or practice ground and you will start hitting shots with your driver at a much higher launch angle which will produce a higher and longer tee shot.