It's tough coming up with names for random NPCs who you just make up on the spot. Some GMs have a gift for it, but most people don't.

One trick is to use one of the many random name generators on the web (fantasy, modern, science fiction, take your pick), pre-generate a list of suitable male, female, (and possibly other) names, and pick one off the list when required. It's simple to do and saves stammering over answering the question, "What's the merchant's name?" whenever a player asks.

If you have the sort of players who like asking all sorts of questions about your setting and NPCs, just make sure you print out a long enough list.

Transcript

R2-D2: All right, I'm out of here.
GM: With the Falcon?
R2-D2: Don't be ridiculous. I don't want to fry in that deathtrap.
R2-D2: I'll take Luke's X-wing.
C-3PO: Be careful, Artoo!
Unidentified Rebel Technician: Okay, li'l fella. Up we get! Into the droid slot!
R2-D2: Wait, who is this guy?
GM: Uh... just some unidentified Rebel technician.
{beat}
R2-D2: Why does your name tag say "Unidentified R. Technician"?
{beat}
Unidentified Rebel Technician: I lost a bet.