How do I know if a surname goes with a first name?

It depends on your genre. If you're writing realistic fiction, your characters should sound like normal people. In fantasy or dystopian stories, your names can get a little wilder, but there should still be flow between the first and last names. You may even see nouns and verbs used for last names in fantasy and dystopian stories. Overall, say your name out loud, and imagine if you can picture someone with that name actually living in the world you create. For example, Jane Windrider might be a name for a pirate or a futuristic astronaut, but Jane Daniels could be an ordinary kid at a high school.