I tend to only name my Sims after I’m finished creating them (this includes choosing their clothes and overall colour scheme). But even then, I usually only choose their first name. As for their last name, I hit the randomise button until a nice name that goes with their first name (and their ethnicity) comes up.
The only time I’ve ever chosen a last name for one of my Sims was with Martin (the Sim in my avatar). When I first made him, I didn’t really care about ethnicity and such, and I went with the surname Rubio (generated by the game). But I decided after a while that he was going to be Irish. I looked up the surname Rubio and saw it was Spanish, so I went and looked up Irish surnames to find one that might go well with the first name Martin. I settled on “Flannagan” which means “red” - to match his passion and drive… and also his hair. :tongue: