Assume the attitude of an onlooker, and let sounds, smells and other stimuli come and go, let feelings and emotions arise and fall, let the thoughts erupt and float about- remain an onlooker. This is royal art of ancient rishis. It is the highest heaven. It is the birth-right of one and all. Holy books, temples, places of pilgrimage, virtuous actions are all mere outside aids for this practice.
But you may say that you get mixed up and there remains no distinction between the onlooker and the thing looked at. Let us see it from another angle. Suppose there is a basket full of fruits. There are mangoes, apricots, oranges, grapes and dates, but there is only one apple on the top. I ask you to pick it up and keep it out of the basket. You keep it apart. Now it is separate, away, not mixed up with other fruits in the basket.
In the same manner, I see, I feel, I think. Though I see so many things and people, feel innumerable feelings and think thousands of thoughts, 'I' am only one. Pick out the 'I' from the basket of the mind and let it stand apart. If it gets mixed up again and you are once more caught up, pick it up and again and let it stand apart. That is the only way. Whenever, the 'I' gets mixed up with the others, pick it out again and again.