...about what you want to observe.
Better observation takes two things, the effort to observe what you want to know. The second is to have more knowlege about what you are observing.
The first part takes patience and practice. The human mind is a reprogrammable computing device. Your mind forms new neural pathways and optimizes existing pathways with practice and repetition. Any task can be subject to this effect from driving to playing sports. Consider the example of learning a card game. I find that with a few weeks of playing I get far better and faster at a game. My mind has formed some neural connections that allow me to process the needed problem solving skills more quickly. these connections are improved and optimized through repetion and practice. If you make a point to get out and regularly practice the skill you desire it will get easier.
The knowlege part is important as the better you know about what it is you are observing the more you will know what to look for and when to look for it. Understanding the what and the why is critical here, even if you do not know what they are to start with. If there is nothing you can read about your subject, no source of ready knowlege you are forced to create it yourself. Keep some notes! This will allow you to go back and check, our human brain can be very bad at remembering critical details correctly, (ask any police detective that interviews witnesses) we color all we see and how we remember it with a very subjective point of view. Keeping notes is a great tool to help you remove the observer bias that will creep in.
Just a couple hints.
Andrew