"What exactly does one do when one meditates, Mr Wang? Do you think specific thoughts or do you try to "clear your mind"? I find it extremely difficult to "clear my mind" of all thoughts. The very act of trying not to think of anything, is a form of thinking."Well, it all depends on what kind of meditation you're doing. However, for starters, meditators usually do some form of concentration meditation. So I'll discuss that.

Whatever the thing is, the idea is that you will keep your attention focused on it. You do not analyse it, you do not form opinions about it, you do not think about it. You simply observe it, and keep observing it.
Inevitably your thoughts will stray. For beginners, it will take approximately 7 seconds before you start thinking of something. You will start thinking about your work in the office, or your brother's new car, or your dental appointment next week. Anything but the one thing that you were supposed to be observing.
Anyway, as soon as you become aware that your thoughts have strayed, you bring your attention back to the thing again. And again and again and again.
One of the very first lessons you will learn is that you are not your conscious mind. Your conscious mind has a mind, a personality of its own and it usually will not be very happy that you told it to shut up for 20 minutes.
Next you will learn that you are not the master of your conscious mind. It may even turn out to be your master. You will see that your conscious mind seems to wander where it will, it simply will not follow your instruction to stay in one spot. It also has a surprising ability to walk away without you noticing, until much later.
Over time, if you keep practising your concentration meditation, you will notice several benefits. The monkey mind can be tamed. One benefit is that your concentration dramatically improves.
This obviously is of considerable practical benefit. For example, if you need to do some work, you can place your concentration on your work, and you will find that your concentration is very solid. It will sit on your work like a physical object, and it won't move until your work is done. You will not be easily distracted.
In other words, if you can concentrate fully, and wordlessly for 30 minutes on a candle flame, you will find it easy to, say, fully concentrate on your textbooks for 2 straight hours. Piece of cake, really.
But that is not what I really want to talk about today. Today, what I really want to talk about is presence in the now.
Being present in the now is a key idea in many different spiritual disciplines. It is literally what it means - your attention is fully aware, fully focused, on where you are right now, and what is happening right now.
In other words, you are not thinking about what happened last year, or last week. You are not thinking about what you need to do later today, or next month, or six months from now. 100% of your mental faculties is focused onto the present moment.
Presence in the moment is an attribute you can practise and develop through concentration meditation. If you are concentrating on your breath, you concentrate on your breath as it rises and falls, right now. If you are concentrating on a candle flame, you concentrate on it fully, right now. You do not think of anything else.
This is how you learn to be fully alive. Because all you can ever have is the present moment.
There is a fundamental spiritual truth here, but it's difficult to express it in words. But it's something you can experience.
The past, you see, is an illusion, and so is the future. Neither of them really exist.
The past is basically just memory. And memory is just the movement of certain electrical impulses in your brain.
The future is basically just imagination. And imagination, too, is just the movement of certain electrical impulses in your brain.
So you only have one place left. That's the present. That's why it is important to learn to concentrate on being fully present in the now. It's the only place where you can live. The more you concentrate on being here, the more fully alive you'll be.
Before anyone accuses me of being unscientific again, I'd better end with a heavy dose of Albert Einstein. In his own way, he obviously understood this fundamental truth too, although his description is on somewhat different terms. Instead of saying that the past and the future do not exist, Einstein says that the past, the present and the future all exist simultaneously:
Albert Einstein and the Fabric of TimeEinstein was a damnably smart chap. Through his physics and maths, he actually figured out lots of things which Buddha only found out through getting enlightenment. Einstein's words - "Reality is merely an illusion, albeit a very persistent one." It's something that could have come out of Buddha's mouth.
Surprising as it may be to most non-scientists and even to some scientists, Albert Einstein concluded in his later years that the past, present, and future all exist simultaneously. In 1952, in his book Relativity, in discussing Minkowski's Space World interpretation of his theory of relativity, Einstein writes:
Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.
Einstein's belief in an undivided solid reality was clear to him, so much so that he completely rejected the separation we experience as the moment of now. He believed there is no true division between past and future, there is rather a single existence. His most descriptive testimony to this faith came when his lifelong friend Besso died. Einstein wrote a letter to Besso's family, saying that although Besso had preceded him in death it was of no consequence, "...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one." Link.
Oh, as for those who want to know more about the interesting spiritual idea that the future and the past do not exist, I recommend this book: The Power of Now. Note that it is not a "how-to-meditate" book, so go look for another title, if a "how-to-meditate" book is what you really want.