Do you have any advice for pointers or punching up dialogue? I've often gotten notes that characters aren't distinct enough.
One piece of advice? In dialogue, the person hearing a line is just as important as the person speaking the line. When writing fiction, you need to justify why Character A is offering information to Character B, using both A and B. The more personal the information is, the more justification you need.
In psychology, there's a thing called Social Penetration Theory. It says that, the less we know and/or trust a person, the less we share about ourselves, and vice versa:
When talking to a stranger, we either stick to social scripts ("How are you?"/ "I'm fine"), or we use conventional conversation topics ("Hate this weather."/ "Same here!").
When talking to an acquaintance, the topics get both broader ("Where'd you get that tie?"/ "Macy's!") and somewhat deeper ("You hanging in there?"/ "Stressed, but still going!") but not too broad and not too deep.
Friendships are marked by having broad shared topics to the point of in-jokes ("Last episode was plusungood, yeah?"/ "Try double-plusungood!") and conversations around real vulnerability ("How you doing?"/ "Today sucks").
It's only when you get to the really intimate relationships — best friendships, long romances, close siblinghood — that you start to see the heavy stuff come out ("I wish my mom supported me more"/ "Yeah, you deserve it").
Note 1: the levels are cumulative — close siblings can talk about almost anything from the weather to their deepest fears. Note 2: sometimes people do violate these norms (e.g. through telling strangers about their romantic troubles), but most listeners find such violations very off-putting.
Anyway, the common error in fiction is the California Conversation: when Character A starts telling Character B on their first date that deep down he feels he'll never be worthy of his father's love. The joke is that the California Conversation only happens in movies because maybe that's how Hollywood people talk to each other, but out in the real world people have a sense of boundaries. If A tells B all that father-stuff after knowing B for an hour, then the audience is going to conclude that a) A's father isn't that important to him, b) A is an awkward over-sharer, or c) this dialogue is weird and unrealistic.
One example of dialogue done wrong: the novel Throne of Glass. The protagonist Celaena is described as tough and aloof, but in an early scene she starts telling a guard she met that same day about how heartbroken she felt to have her hair cut off when she was sent to prison. There are several things that feel off about this moment. We humans do not, as a rule, tell near-strangers about things that break our hearts. A hardened assassin trained in secrecy seems especially unlikely to share like this. And a guard who is holding said assassin against her will seems like an especially unlikely target.
This kind of disclosure can come off like info-dumping: the author wants us to know the hair is important, so the character blurts it out. It can come off like social incompetence: maybe Celaena doesn't understand boundaries, which would be an interesting flaw if it fit with her other characterization. It can come off as implying that the subject isn't important, because if it was then you wouldn't tell a guard about it during your first meeting. Not ideal.
One example of dialogue done right: the novel What Could Be Saved. It's about a brother and sister rebuilding their relationship as adults, after the brother disappeared as a child 50 years ago. The brother's deepest disclosure [SPOILERS] is that, after he was kidnapped by Thai insurgents trying to get leverage on their American spy father, his captors told him that his family refused to ransom him. Being 11, he believed this and chose to run away rather than return home when he did get free; it was only much later he began to question that story enough to try and contact his family [SPOILERS END]. But it takes the entire friggin novel for the brother to build up to telling his sister that. Over the plot, the siblings go from stilted small-talk, to casual chats, to half-remembered in-jokes, to serious conversations, before finally feeling comfortable enough to edge their way up to the reason the brother never returned after his escape. That disclosure, when it finally comes, is a gut-punch. An earned gut-punch. A gut-punch that caused me to tear up, because I was on the entire journey it took to get these characters here.
If you don't feel like spending an entire novel building up to one conversation, simply establish who the characters are to each other before they start talking. A classic example is the story "Hills Like White Elephants." It's a stifling near-horror story about a man pressuring his girlfriend into an abortion, only no one ever uses the words "abortion" or "pregnancy." Not only does the couple's growing distance come through in their inability to discuss the issue directly ("'It's not really an operation at all,' the man said... 'It's just to let the air in'") but we see the woman repeatedly respond to her partner's assurances with "They're lovely hills... look like white elephants" or "Can we have another beer?". She's losing trust in him, so she's resorting back to small talk. Her discomfort is palpable, even though verbally she agrees with her partner. We learn a lot about him, and about her, through what they don't say to each other.
One last example: FBI tapes. NYTimes has an excellent set from January 6 rioters, and there are a lot of other transcripts around. They're interesting because they involve experts trying to get personal disclosures out of strangers, which ends up being the verbal equivalent of trying to pin down a drop of mercury. In the January 6 set, there is video evidence of the crimes, but there's still a ton of verbal dodging and distracting and soft-pedaling in the face of undeniable guilt. Note what words real people use when making real disclosures that personal, and note what they don't say. That's how dialogue works, and that's how you can inject characterization into your dialogue.