The 100m is a very intense and technical race. Initially the athlete should concentrate totally on his starting technique which he has fine-tuned in training. Irrespective of the lane or adversaries, he now focusses on a smooth acceleration towards attaining his maximum speed. Once he has attained his top speed, he now relaxes totally in order to maintain his speed with the least amount of unnecessary interaction from muscles or parts of the body not being used for sprinting. The finish also requires some thought because a centimetre gained by a correct finishing technique can win a race, an positive and active forward lean can help to achieve that, althopugh the timing is cricial.A reasonable sprinter suffering from nerves and tension could lose up to 0.6 sec in a race and a novice even more. The top sprinter performs equally well in heats and finals, it takes a lot of work to achieve one’s best, be smart. 

No athlete can maintain his top speed for longer than about 30m, hence the need for tactics in a race over 200m.The start is similar to the 100m, although the acceleration is moderated and the athlete then tries to maintain his near maximum speed using  the most relaxed and economical technique.When the finish line comes closer and fatigue is felt, more concentration is required to maintain top speed and stay relaxed. The finish is similar to the 100m. 

Similar tactics are required as for the 100m.The hurdler will use  a  stride pattern to the first hurdle ,as perfected in training. The 3-stride rhythm with the necessary adjustments is essential for a good race and the finish is similar to the 100m race.

The start is definitely more relaxed than for the 100m or the 200m, but maximum concentration is essential for the whole race. 
A relaxed start which prepares a smooth race saves more energy for the last part of the race which is the toughest in any sport. The difference between the best 200m time and the initial 200m is in general between 0.8 to 1.0 sec. Wind assistance or resistance will automatically change these parameters. 
Athletes should normally adjust tactics according to their strengths and weaknesses, ideally a smooth acceleration over the first 30 to 40m would give one's ideal speed which should then be maintained during the race