I just critiqued a chapter of someone’s work that included three pages of non-stop dialogue with no action, no internal dialogue (or should that be internal monologue?), and no description of the room. It was aggravating and confusing.
Talking Heads don’t exist in real life unless they are yammering on a cable news channel. Things are always going on around your characters. They are never in a blank physical space and nobody has a three page conversation without interruption.
If your characters are in a hospital room, there are machines beeping, codes being called, doctors being paged, antiseptic smells, bland food, cups of Jello, florescent lights humming, televisions on in other rooms, nurses passing by or coming in the door. We don’t live or talk in vacuums. Don’t overdo it, but give enough to settle us into the space.
And a conversation in real life would never go as long as it takes for a three page back and forth without pauses. Someone has to stop and think of what they are going to say next. An awkward silence happens when someone deals out too much information, or not enough and your main character suspects they are lying.
Nobody talks for extended periods of time without breaks in the conversation — except that one guy we all have in our lives, but he’s annoying and we don’t invite him to parties.
As for actions between dialogue, make sure they are relevant to the scene. Is your character anxious? Maybe she’s tapping a pencil. Is she ready to get going on a new clue? She’s probably fingering her keys. Is she excited, interested, bored? Make sure her actions give depth to what’s happening.
This is also a good way to avoid telling your reader everything instead of showing them. If someone has to consciously stop their leg from jumping, the reader knows they are anxious, so you don’t have to say it. (And, yes – I am a firm and adamant proponent of the singular, non-gendered ‘their’)
Do you need to casually introduce an object that’s going to be used as a murder weapon later? This might not be a bad time.
Make your characters real people, give them real surroundings, and real actions.