Depends on player interest, too.
It helps to give the players something to bite at. In the past, what I've done instead of saying, "OK, you picked up six passengers," was to give the passengers a quick description. Instead of six passengers, I just come up with something real quick--right off the top of my head.
"It's passenger boarding time, and you see human family of five waiting outside the ship. It's a man and woman, plus three children--two boys and a girl. The oldest boy looks to be around seven, and the other boy looks to be the youngest, probably about four or five."
As they come aboard, you hear someone yelling at the corner of the starport. "Wait! Wait! I demand you wait!"
It's spoken in Anglic, but it's a rough, gravel-like voice. As the being sprints closer, you can see it's your last passenger, a male Vargr.
And, I'll just leave it at that. Many times, that's enough to spark some roleplay with the players, either now or during the trip in J-Space.
Sometimes I provide a quick description like that above, and that's it. Nothing else happens. It just gives the players an idea of the passengers. They would react differently, I know, if I described six men in their late 20's and early 30's, all human, all physically fit, and all with military crew cuts. I say that, I can guarrantee myself some roleplay time as the Captain will want to know more about who he's taking on his ship. I've had PC Captains forgoe the revenue and not take any passengers on a trip because of this.
During campaigns, I'll sketch out some passenger ideas as they come to me. I keep this and refer to it sometimes in a game so that I'm not always making up similiar passenger types.
The Steward position on a ship becomes one of the more sought after positions among the players in my game because of the way I'll play this. The Steward is the one that interacts most with the passengers, and typically, that character will become the defacto head of onboard Security.
The Gunners usually make up the head of "ship security", with the steward as their chief, though the position is not formal. The same group acts as cargo hands with the Steward as deck master, in charge of everything brought aboard the ship.
There's a lot of roleplaying to be had in that.
Sometimes, I'll just breeze over the passengers with a quickie description, "A family of five, three children, and a male Vargr." And, that's all. We move on. Sometimes, it's a
little more, like what I describe above. And, sometimes, I've got an elaborate scene I want to play out as part of the adventure.