"Make the name pronounceable. It’s annoying if the reader has to sort of mumble over the name in her head every time she comes across it. If you’re writing something historical, try to find accessible names that are still historically accurate. Áed and Máel-ruanaid may have been popular guys’ names in early medieval Ireland, but readers will probably feel more comfortable with Conall or Dáire (and you may not feel like you want that accent mark.)
Make it believable. If your characters have to discuss the name at length (“Why did your parents name you Devyl?”) consider the possibility that it’s too far-fetched. You might like to balance a more unusual name with a boring last name (Indiana Jones), or vice versa (Mary Poppins). If both the first and the last name are fanciful and evocative, the result can be eyeroll-inducing (Bella Swan, Anastasia Steele.)"