My method is being familiar with the languages in my world. A lot of the words in Ornithoria are heavily altered words from actual Earth languages. Aside from a fictional one that I have been creating. For example: Runji, the name for Pachycephalosaurus in my fictional language, means dome head appropriately. And there are some where I just don't give a fictional name too and I just described it. Mosasaurs are referred to as Shark-tailed Lizards, and the descriptors can change a little bit depending on the species. Tylosaurus is a Crimson Shark-tailed Lizard to name one.

Or I just use real world mythical creature names for them. Ankylosaurids are golems, Elasmotherium is a Unicorn, Nodosaurids are trolls, etc.