Top 10 Basic Driving Mistakes :

Mistake #1: Improper Driving Position
The proper driving position is important because it helps you get the optimal feedback from your car's chassis while also keeping you from getting fatigued.
First, your seat should be adjusted so that you are able to depress the clutch completely and perform heel/toe braking without banging your knee on the steering column. You should also be able to use the dead pedal for support through high-g turns. Your shoulder harness should be tight so that you do not need to rely upon the steering wheel for support.
Next, you should have a 90- to 120-degree bend in your elbows with your hands in the proper 3 and 9 o'clock positions on the steering wheel. This will allow you to make a 180-degree turn of the wheel when you need to correct an oversteer slide.
Ideally, your thumbs should be in contact with the 3 and 9 spokes on the steering wheel. This gives you more direct feedback from the front suspension in case of an understeer situation. (Note: Since formula car and sports racer steering wheels are smaller in diameter, your arms should be straighter and have less bend at the elbows).
Finally, your butt should be tucked firmly into the seat back so that you can get feedback from the chassis and up through the seat. This will give you a better feel as to what the rear end of the car is doing. In keeping with the Zen philosophy of racing, you should become one with your car. Get comfortable, go faster.

Mistake #2: Failure to Look Ahead
The most common driving mistake in both autocross and road racing is failure to look far enough ahead.
As street drivers, many of us become lazy and look only between the A pillars (those down posts which border the edges of our windshield). On a race track, because of the planning and high speeds involved, this will not get the job done. You must condition yourself not only to look much farther ahead, but out the left and right side windows as well.
Entering a corner, as you are doing your braking and downshifting, you must be looking ahead to the apex of the corner. Before you reach the apex, you should be looking ahead to your track-out point. In "S" turns, often you have to be looking ahead to the second apex, rather than the corner you are in. In this case, you must trust your peripheral vision to take care of the first apex.
The rule of thumb is, "The faster the car, the farther you must look ahead." The malady of "driving off your hood" is one that relegates many race drivers to slower cars while other competitors make the transition to higher powered cars with ease.
If you are limited in terms of track time, practice looking much farther ahead and out side windows as you negotiate off-ramps and corners on back roads. If looking ahead becomes habitual, you are much more likely to use the technique on the race track. And no, I am not advocating that you adjust your street driving speed upward to match your newfound, long-range vision. That ticket is on you.

Mistake #3: Improper Braking Technique
If you often brake too early for a corner, you may find that looking ahead will cure your problem. When you know where the apex and track-out points are located, it is much easier to know when to ease off the brake pedal and precisely how much to release it. However, you may have other braking problems which do not vanish so easily.
Some drivers brake hard enough in a straight line to slow their car down for the corner, but then they totally release the brake or go to the throttle before they get to the apex of the corner. They transfer the weight off the front tires and onto the rear wheels just when they need their steering the most. This can cause the car to go into an understeer skid. 
In order to keep the weight on the front and the tire contact patches expanded for optimal steering, you should use trail braking. Trail braking is simply continuing to apply a diminishing percentage of braking until you complete your turn into the apex. The transition from trail braking to the apex and the application of throttle to the track-out point should be smooth and seamless so as not to upset the chassis.

Mistake #4: Improper Downshift Technique
More correctly, this should be called "Improper Brake and Downshift Technique," since it is difficult to separate the two. I would like to explain the entire sequence of heel-and-toe braking and downshifting; that would be an article in itself, however, so I will not.
Simply put, the theory of the heel-and-toe downshift is this: When braking and downshifting prior to a corner, you must brake in a straight line while simultaneously clutching the car, revving the engine to match the speed of the drive wheels, putting the car into a lower gear and then releasing the clutch without upsetting the tire contact patches and suspension in the process.
For those of you who do not know how to heel-and-toe downshift, you may want to go to Bob Bondurant's or Skip Barber's driving schools. For those of you who know how to heel-and-toe downshift, but are still not doing it as smoothly as you would like (i.e.: you are chirping the tires when you downshift), here are a few tips:
· With your car in neutral and with the engine running, practice putting pressure on the brake pedal with the ball of your foot while swinging your heel and the outside of your foot over onto the gas pedal. Please, do not touch the shift lever!
· Using constant brake pedal pressure, try to rev the engine up to a reasonable rpm and hold it there. Repeat the process, pivoting your foot from left to right until you feel you can do this with consistent repeatability. Your tire chirping problem is probably due to your lack of revving your engine up high enough or blurping the throttle and downshifting too slowly.
· Practice your downshifts at your next autocross event or on an uninhabited back road. Better yet, take a refresher driving school course until you have your heel/toe downshift perfect. Good braking and downshifting is essential if you want to improve your lap times. (Not everyone, however, is impressed with a good heel/toe downshift technique. Mr. Holland, my high school driver education teacher, marked me off for doing it.)

Mistake #5: Apexing Too Early
On most race courses, there are far more late-apex corners than early-apex corners. So, if you want to be successful in autocross or road racing, you had better get used to learning how to drive late-apex corners. At driving schools, where cones mark the turn-in points, apexes and track-out points, you may not have a problem. But what about driving an unfamiliar track? For a better understanding of this problem, please refer to the illustration below.
There is an easy way to determine the location of the apex for a corner. Work backwards from the track-out point, to the apex, then to the turn-in point. Ideally, you want to exit the corner in as straight a line as possible. This will help you maintain momentum and maximize straightaway speed.
When dealing with more than one corner (See illustration below), where the last corner in the series leads onto a long straightaway, you must often sacrifice your entry speed into the first corner to get more exit speed off of the last corner. It is better to "go in slow and come out fast" when exiting onto a straight.
Apexing too early is the number one killer of straightaway momentum. The symptoms of apexing too early are as follows: You turn into the corner where you think the apex should be, but upon exiting the corner, you find that you need excessive steering input just to stay on the track. You have major understeer and you are scuffing off way too much speed at the track-out point as you exit the corner. Go back and study the line of this part of the track again. You may be apexing too early.

Mistake #6: Premature Acceleration
If you are not apexing too early, you may be suffering from premature acceleration. While embarrassing, premature acceleration is not a condition you have to live with forever. However, the cure does require patience and control.
It is not enough to brake and downshift properly and turn into the apex at the right point if you still are going to apply the throttle too early in a corner. Be patient. Trail brake long enough to get the nose of your car pointed at the apex and aligned with your track-out point. Why accelerate before you have the car pointed in the right direction? When you transition to throttle, do so smoothly without upsetting the chassis, but be ready to go to the throttle when you reach your last apex and the car is pointed down the straight.

Mistake #7: Not Using the Entire Track
If you watch professional F1 drivers, you will notice that they use every last inch of the race track, including the flat curbs. All too often I follow students who have great technique but who do not use the entire race track. This hurts their lap times tremendously. When asked, "Why aren't you using the whole track?" they usually respond with surprise, "I thought I was."
At some time during practice, you should touch the curbs slightly so that you know you are using the entire track. Next, you should find out which of the flat curbs will help or hurt your lap times. Racing is a game of inches. Inches become tenths of a second. A tenth of a second on each corner can turn into a full second per lap.

Mistake #8: Failure to Compensate for Slip Angles
Everyone knows that race cars slide or drift through corners, but not all race drivers completely understand the effects of slip angles or the direction of drift.
If you are braking, downshifting and turning into a corner correctly, but are still not near the apex, you may not be compensating for the slip angle of your car. Perhaps you are aiming for the apex cone, but you just cannot seem to hit it correctly.
The fix may be relatively easy. Aim behind the apex cone, imagining a "false" or "phantom" apex cone is there. By compensating for your car's slip angle, you will probably hit the apex precisely. This may take some experimentation as you may compensate too much or too little for the slip angle while finding your phantom apex.

Mistake #9: Killing your Momentum in Traffic
While this driving mistake does not apply to autocross racing, it is most definitely one of the most common and frustrating problems for inexperienced race drivers. Getting boxed in. Losing your momentum. Getting stuck behind a slower car. Being unable to pass for a lap or two. Does this sound familiar?
The best solution to this problem is early recognition of the slower driver. Notice where he is on the track now and where he most likely will be when you want to pass him. Depending on your race pace, you may either need to speed up or slow down to pass him at the point where your momentum will not be diminished dramatically.
You may have to hustle and out-brake the lapper before the next series of slow "S" turns, or you may have to lay back a little and build momentum off a turn to pass him on the next straightaway. This is perfecting the art of looking ahead to the max.
If you get extremely proficient at this technique, you can use it to strategically sandwich a car that you are passing between you and a car that is in hot pursuit of you. Not only can looking ahead be used to maintain your own momentum, but it can be used to kill someone else's momentum. When it works, it is truly a thing of beauty.

Mistake #10: Poor Weight Management
Small tire contact patches are all that keep you from leaving the track. The faster you go, the more critical your contact patches become. Fast race drivers are masters of weight management. They shift weight smoothly and seamlessly from front to rear, from side to side in an effort to maximize traction and maintain speed around the track.
Great weight management requires an empathetic connection to a car's suspension and those tiny little tire contact patches. Smooth braking. Smooth throttle. Smooth weight transition while at speed. Balance. Touch. Feel. This is what separates the great drivers from the near-greats.
Once you have read all of the books on race driving and after you have learned all of the proper driving techniques, racing ultimately comes down to a couple of factors: How well you are communicating with your race car and how much in synch you are with the race track. Hopefully, at some point in time you will be able to concentrate less on the minute details of driving and start feeling like an artist who grows more confident with every bold brush stroke he puts down on canvas.