Unbelievably hard, at least to me. I have no idea how other writers do it and at least in most cases make their different characters sound reasonable and not out of place. The names I'm creating (and been helped to create) are starting to sound reasonable as well, but at first they sound so utterly ludicrous that I just end up scrapping them on concept alone.
Ught, I'm only cut out for making melodramatic names, Like Brutilus Bloodborn.
On the plus side, only four minor character surnames (which can be put off till later, as they are only used for one big sequence) and a ship name to go.
Edit: and done. Names are hard.