A Few Best Ideas

Question:
What are some of the best ideas told by OSHO Rajneesh?

Ans: Osho is an ocean. And within this ocean, you have so many invaluable gems that it will be difficult to make a count. But you have asked what are some of the best ideas told by OSHO Rajneesh? I can understand the intention behind your question. You want a quick-fix. You want an instant band-aid that you can wrap around whatever it is that your life needs at the moment. And you are not to be blamed for it. This is the kind of age we live in. We tweet instead of talk. We google instead of read. And so on and so on. And not that there is anything wrong with it. It is just that the quest has to be taken to the next level. It is one that will require you to experience it. 
Buddha always asked his disciples to believe in experience instead of faith. He said, "Do not believe anything I say unless you yourself have experienced it." He was against blind faith. Which is why he never even mentioned the word 'God'. Unlike all other religious leaders, he never asked one to be faithful. He was one for experience. In fact, I do not see it fit to mention the Buddha as a religious leader either. He was beyond all definition. He was like a doctor, a healer, he healed people. And so did OSHO.
But you have asked what are some of the best ideas by him? There is no best idea by definition for everyone will have a different need. Everyone is unique and whatsoever idea was given by OSHO was based on the person who asked the question. The same question could be answered by OSHO in two different ways, if it were asked by two different people. And it will very much depend on the nature of the person as to what s/he describes as the best idea. What seems good to me may not seem very good to you.
So, I will be careful before using the article 'the'. Yes, I can tell you what I thought were some of his best ideas. This is only me speaking. Others may have a different list altogether.
I once heard OSHO say, "You are already that which you are seeking." He quoted the Upanishad and said, "What we seek is as close as it is far." The matter seems contradictory but it is true. Nothing on this earth is more important that realizing ourSelves. There is nothing else that we have or will truly have except our own selves. But while people have piled up umpteen number of other inessential commodities, they have gone farther and farther away from themselves. Their true selves. Their innocent selves. Their pure selves. We are our only friend and our only enemy. To get to this Self, OSHO wanted us to just stop where we are. To stop this race and be That. Have you ever wondered how people are madly after a chase that is never-ending? One goal achieved and the next one begins. One aim met, another one set. 
There are two ways to stop this wild goose-chase. One when we know that the desires are not conquerable. The 'Grapes are sour' syndrome. We realize that we could not win so we say that the thing that we wanted to conquer was not worth conquering anyway. Here, we don't even have the courage to admit that we failed, that we lost. Because we are too proud, too arrogant to do so.
The other way of stopping is to know the futility of that which we desire. To know that even if we were to achieve what we wanted, it would mean nothing. We would still thirst for more. It is a mad, a paranoid quest with no end. 
This is truly stopping. In fact, the happiness which you want to gain by achieving whatever it is that you want to achieve isn't out there, it is right inside you. Have you ever wondered how a dog finds pleasure in a piece of bone, a cat is fond of eating rats, and you, maybe you like watching Saturday night Live, something that a cat or a dog will find completely incomprehensible. The thing itself is not good or bad. It is YOU that makes it so. It is something inside you that makes it so. What that Something is, I can't say. But that it is there, it is certain. And with mindfulness you will get to that point. 
But for mindfulness, you will need to learn to be present. Not in the past or in the future which is where everyone seems to be but right here, right now. Doing whatever it is that you are doing and squeezing the very life out of it. Doing only that and being nowhere else. Buddha said that when you walk, look only at the next four steps to be taken. That is enough. You will complete your journey this way. 
This, indeed, is true meditation. This is the true form of awareness. After that you don't even need to go and sit in meditation for 10 minutes or 15 minutes. Your whole life, every moment becomes a meditation. 
Swami Vivekananda said that that life moves from imperfection to perfection. He was wrong. Life is perfect as it is. Nothing needs to be added to it. It is enlightened right now. It doesn't move from imperfection to perfection. It moves from perfection to perfection. If you can understand, that you are already that who you seek to be, you don't need to remember anything else. This will be enough.