I need your opinion

[ATLBrvs326]

Like Ive said before I am a relatively new official, but just now got serious. I need some help on a issue that I have. This is kind of vague, and I expect to get different point of views. I am not really sure what to be "thinking" when I am refing off-ball and then on-ball. For example, this happens to a lot of officials, but I am just looking around, and then out of nowhere, someone trips and I have no idea what happened. Was it a block, was it a charge, etc.? So that is my question, what are you thinking when you are watching the paint? Also what are you trail when on-ball, ect. I know all of this will perfect with experience, but I need to learn what it is I need to be doing. I have 5 games tommorow, so I will practice all of this. (also quick question, what do you prefer: rulebook or officials manual?)