ok, so like with everything, I'm prefacing this with "this is what works for me". I'm also gonna say, I'm writing this directly in tumblr, so my grammar in my dialogue tags and shit is probably gonna be wonky. Whatever.
Dialogue is informed by two things: the speaking character's.... uh... character and the context of the situation. These things will not only influence the physicality of the dialogue but also what's emphasized in it.
The same line can be delivered in many different ways, depending on those factors.
EX: "Oh, I see," he said.
"Ohhh, I see." Grendel slowly turned towards Ruby. He might not have had eyes beneath that tattered blindfold, but she swore she could actually hear them rolling as a thin, sardonic smile pulled across his face.
"Oh." Dem's voice was very small. He dug his palms hard against the railing before continuing. "I... see."
"Oh! I. I... uh. I see!" Tey said. That was a lie. There was nothing in any part of his delivery that convinced Emmrich that he did, in fact, see what he was talking about.
Ben had to press his lips together, hard, to keep from squealing. "Oh. Oh." Ever so carefully, he knelt down and offered his hand to the little creature before looking up, tears gathering in his smiling eyes. "I see."
"Oh... hurm. I see," Aurin mumbled. He leaned forward to inspect the relic with a sound not unlike a butter knife being dragged across a cheap plate.
Now, like, not every bit of dialogue needs to have an expository bit attached to it. And in long conversations that can get a little tiring, I think. So I like to think about how the back and forth will look. Sometimes just as important in a dialogue is what is happening when the characters aren't speaking. (borrowing @ltleflrt's Caelnir for one of these)
"Oh." Dem's voice was very small. He dug his palms hard against the railing before continuing. "I... see."
Cael looked around the room, anywhere but at his best friend. "I'm sorry, Dem."
It had to be the heavy, damp air that made the words stick so hard in his throat.
"Yeah. Yeah... me too."
"Ohhh, I see." Grendel slowly turned towards Ruby. He might not have had eyes beneath that tattered blindfold, but she swore she could hear them rolling as a thin, sardonic smile pulled across his face.
He leaned in close to her, so close she could smell the metallic tang of his skin. So close she could smell the distant smoke of the first fire those first humans clustered near on his breath.
The lizard deep in her brain started screaming.
"Grendel," Caim warned from his perch.
"I see, Ruby Jones." Grendel said. "Do you?"
Oh! I. I... uh. I see!" Tey said. That was a lie. There was nothing in any part of his delivery that convinced Emmrich that he did, in fact, see what he was talking about.
"Do you, my dear?" Emmrich tried very hard to not use a professorial tone around his Rook. They were equals, and the younger man was certainly more learned than he was in many other things. But he could tell by the way he flinched that it had slipped out.
Tey's gaze darted around at the gathered members of the Mourn Watch. To Emmrich's eyes he seemed so alone in this moment, Crow's leathers bleached grey in the pale green light, surrounded by a horde of academics, the undead, and several examples of both.
Suddenly, Emmrich wished he'd asked this more privately. But before he could apologize, a hissing skeleton clattered by at high speed, chased by a pack of aggressive wisps.
"Ok. No. I don't understand any of this. I was just gonna try and grab some context cues as we went on." the young man laughed. "Just tell me what needs doing."
So, short form, dialogue for me isn't something that can happen divorced from any physicality in the story. And I know there are folks who disagree with the habit of italicizing words for emphasis.
I do it, i think, because I come from comics, where there is the tradition to break up word balloons visually by emphasizing some words in bold. It makes sense to me from a visual standpoint, to call out where the beats would land when someone's speaking.