[quote=@Hawthorne]
So I was wondering... with each character coming from different backgrounds (some are from the military, some are mercenaries, some are unaffiliated)... I wanted to ask if there's a galactic standard for identification over comms? I've mostly been using callsigns when referring to myself (Castle, in this case), and family names for everyone else, but should I be using Orbital Designations? Model numbers? A mix? 
[/quote]

Here's where we run into personal preference, mostly. It's the flip side of making it broad enough that people can make up whatever background they want. 

The simplest answer is that any of the above are fine, depending on how you think Holden would handle it. When we start getting real combat I'll introduce a very loose guideline in-character for it, but even that is really going to come down to how you all want to handle it.