I'd suggest you don't ao much try to avoid it happening (it will anyway), but simply try to keep players "in character" as much as possible. 


Confused, distracted, interrupted table conversations can be seen simply - as in real life activities that require co-ordination and group decisions - confused, distracted, interrupted conversations between people (i.e. PCs). 

Sometimes you have to interpret a little (e.g. "did you write that potion on your character sheet" is interpreted as conversation nearer to "can you remember what the potion is that's in your backpack?" -- but you should constantly encourage questions framed the second way so that the conversation is plainly in character; eventually some players will do that, and it works much better)

So "Hold on, I'm talking to this other guy" is assumed to be *in character* conversation. So while you might say "Do you wait?" or "I assume you're still doing what you said", you might instead say (taking the role of an NPC) "Who are you calling '*this other guy*'? My name is *Mister* Tibbs!", or you might describe an event that occurs *while they're talking* -- *While the two PCs are distracted by their conversation, two boars run squealing from undergrowth in the forest, and they're headed right for you. They seem to be runnning in a flat panick - in fact they don't seem to even realize you're in their way. *You* have maybe two seconds to fire your arrow or jump aside. *You* are further back and have an extra second - you could try to run a few paces to be out of the way."

.... and so on. 

Then when the action-oriented players have stated an action (as they usually do), if they don't choose to stop, they just *happen*: "While you were conversing with Mr Tibbs, Jasko the archer continued into the forest; you can't see him."


Such muddled conversations and potentially uncoordinated actions will naturally occur, but you can refashion them into being conversations and actions that are happening in-world. If you're fairly relentless about this reinterpretation and redirection (at least as far as you reasonably can) - it keeps directing players back into acting in character, and the muddle and confusion of their choices of actions is then just part of how they act in their group. Keep things moving along.