One thing writers will hear a lot about but rarely discuss is Point of View (PoV). We are most familiar with this when we write first-person PoV. In that style, everything comes from our frame of existence, all discussion being our own thoughts, actions, and experiences. However, there are a few other perspective we can write from, and I would like to focus on one in particular - third-person character PoV. We see this used a lot in larger, sweeping epics where there is more than one main character, and it can be very effective. However, it is not as easy as just writing about someone else.
Paul thought long and hard before coming to his decision. "I just can't do what you ask," he told Abraham while shaking his head. Paul stood up and walked out of the office, shutting the door behind him. Abraham remained at his desk, his heart filling with regret about what he now had to do.
A simple scene, four little sentences and not a lot of moving parts. We get an interaction, one character reacting to a situation, then another character left to consider the consequences of that action. Very straight-forward writing, and all in the third-person perspective. Not a lot to work with, one might think. However, let me ask one simple question.
Whose perspective is this story from?
In simple third-person perspective, we take the story from one person's perspective - Paul or Abraham in this case. However, in this paragraph, no matter who is in charge of the perspective, we have a PoV violation - we betray the third-person rule. How? Well, if this is all from Abraham's perspective, we can't talk about how "Paul thought long and hard" because Abraham would have no way of knowing what's going on in Paul's mind. Conversely, if this is Paul's perspective, he would have no idea what Abraham did or felt after Paul left the office. In either case, the scene slips out of the character's perspective.
Now, there are versions of third-person writing that allow this. Third-person omniscient allows the reader to see and know everything, and there's fly-on-the-wall style, where the reader is just witness to everything but not in anyone's head - often referred to as TV show writing. These have their advantages, but third-person character writing gives the reader an opportunity to engage the story from one perspective, and ride along from that view. It's effective in that well-done third-person PoV places the reader in a very specific place in the story. However, violating the boundaries demanded by that style dispels the illusion cast upon the reader, and cheats them of an experience.
The secret to writing from one character's perspective is for the writer to "see" the story from whichever character holds focus, and engage the other elements from one specific mindset. This is often done only by practice, frequent mistakes and constant corrections, and another reader always helps. But it's an effective tool to master, and well worth the effort.