'The greatest deception men suffer is from their own opinions.' -Da Vinci
True observation means to see (or perceive) the object in its entirety and without any bias. Can we do that? Often we project our own nature on the object of our observation. Our observation then, would not be unbiased or in some cases (where the projection is too much) our observation would tell us more about ourselves instead of the object.
Do not search for reality in your own theories (or conceptions or spiritual texts), but forge theories and conceptions from observing reality.
One may wonder how to do that. How to truly observe? Consider a simple example: You are listening to a someone who is explaining a complex phenomenon, but at the same time, you are also thinking about what he is saying. Would you be able to understand what he is saying completely? Or would you understand it more deeply if you listened to him in complete silence, without thinking about anything at all? As you may have understood, often your mind itself is an obstruction in your observation.
To stop your mind from clouding your observations, one needs to quieten the mind. The more quiet the mind, the more are the chances that the observer will notice something that he could never notice before. He could see the object from all perspectives he wants and is not bound by his own thoughts.
But then the question arises how to make the mind quiet? Granted that one may not be able to stop thoughts when he sees something relatable. But anyone should be able to 'not think' upon observing things he does not relate to- things that are not of concern for him. One may observe everyday objects and try not to label them, not to judge them, but just observe without thoughts. By objects, I mean absolutely anything- things, processes, concepts, sounds, people, etc. But start with simple objects. The most simple subjects of observation can be found in nature. It is easy to observe nature truly because nature does not trigger your mind often. If one would start with simple objects, eventually he will get better control while observing more complex objects.
When he sees objects as they are, his ability to observe will improve and then he will find himself watching his own thoughts. He will be able to observe any reaction of his mind while being completely separate from it.
Thoughts cannot teach you that which silence can.
Another aspect is your awareness. Even if your mind is quiet, but you are well into sleep, you obviously won't be able to observe anything. In fact, the only thing we have ever done our entire lives when we drop the mind is- sleep! No wonder why so many people feel sleepy after 5 minutes of meditation. Maintaining your alertness while leaving your grasp on the mind is necessary to improve your observation.
So, pick a time of your day when thinking can be minimal and you can maintain your alertness. Maybe when you ride the bus, or having lunch, or maybe when you take a shower- be aware and observe everything that is happening around you and within you.