Scanning is about looking quickly through a crowd or some other complex arrangement of people and objects. The aim is to find a particular person or object. This is best achieved by narrowing your attentive focus to a set of shapes or patterns that are unique to your target. For example, if you are searching for your friend who you know is wearing a red dress, look through the crowd quickly while only trying to spot red things. This significantly improves your chances of finding your friend quickly.
There are exercises that are performed to improve scanning performance. For example, it is helpful to practice performing smooth eye movements across the crowd. Jerky movements increase the likelihood that you will jump over your target entirely. Try choosing an object to find in a crowd, selecting an identifying feature of your target, and smoothly move your eyes across the crowd looking for your target. If you perform this exercise regularly, you will find your scanning improves.
Tracking is about keeping your eye trained on your target as it moves around among other persons or objects that are all fighting for your eye's attention. If you have already found your target by successfully scanning the crowd, there is no longer any need to pay attention to the flurry of objects surrounding your target. Thus, tracking is best carried out by pretending that those distracting objects do not exist and focusing your attention exclusively on your target.
There are also exercises performed that serve to improve tracking performance. For example, choose a bright object and ask a friend to drop it from a height of three feet. Follow the object continuously as it drops to the ground. After a few attempts, increase the distance at which you must track the object. Continue to increase the distance after a few attempts at the current distance. It may also be helpful to reduce the brightness of the object dropped and to drop objects that fall to the ground quicker.