The trick for me is looking past the dictionary of fantasy names. I stare at a map, pick geographical features, and mess with the syllables. A mountain range called the Vael Tor? That's a person now—Vaeltor, maybe Torvael. Place names carry instant history, like they've got soil under their nails. I stole a side character's name from a mispronounced street sign, 'Elmhurst,' which became 'Elmhur,' and suddenly he was a woodsman.
Another angle is to borrow from obscure mythologies everyone else overlooks. Instead of Norse or Greek, dig into Basque folklore or Sumerian creation myths. You get sounds that feel ancient but fresh, like 'Irkalla' or 'Ekhi.' Just say them out loud. If it trips your tongue three times, it's probably good; it forces the reader to slow down and taste the word, which adds weight to the character.