So, how do you? Especially last names?
Several ways. For standard US names, I often stick with the basics. Occupational names, such as Baker, Cook, Carpenter, King, Candlestickmaker, and so on. But you can also grab a phone book and randomly open a page and stab a finger to find a name.
For foreign names, I'll sometimes look in the various lists of foreign name meanings. Then pick a name that might have a meaning for the character.
My favorite though is to go back to my own list. I keep a running list of random names I've thought of, now in OneNote on my computer, tablet and phone, synched through Microsoft Office 365. I've pulled character names, pen names and other things from this list. These are names that just sound right for something, like Elroy (Roy) Higgins, Bettina (Betty or Tina) Hutchins and Rafael (el Tigre or Tiger) Machado. Haven't used those yet but they've been in the list for a while.
Last option, pick names that are on the most popular boys/girls name lists for the year/time frame the would have been born. Names like Tiffany, Amber, Ruth, John, Paul, George and Ringo.
Pretty much though, if you can't think up a name, then you're probably not that good at thinking up a plot or even a premise. And a name is a lot easier to change halfway through the book than the plot or premise is.
Though a quick lesson here. A thousand and eight years ago, before word processing software was mainstream, I was at a tech demo of the then new Word Perfect software. The sales/tech/demo guy showed how easy it was to change the phrase "complaints to customers" to "complaints by customers", which occurred multiple times in the demonstration memo. Replace "to" with "by" and the document instantly changed every instance of "complaints to customers" into "complaints by cusbymers." You don't want your protagonist, Bill Harkins from Billings, Montana to become David Harkins from Davidings, Montana.
Jeff