Adding to the above, books are a really great source that also provide a 'natural' theme to naming. I commonly take names out of novels I've read recently, so if I've read Jane Austen, names like John, George, William, Emma, Jane, Isabella etc. will abound. After reading 'Howl's Moving Castle', there were Howl and Sophie (of course) as well as Michael, Martha, Augusta, Calcifer, Lettie... whereas 'Dracula' had Jonathan, Mina, Lucy, Arthur, VanHelsing
and some more. It's really easy to take names from established characters and choose traits accordingly.
On other files, I assigned colours to families and named them based on my associations with said colours. This gave me names such as Raven Noir, Cinder Flamma, November and December Ice... which went in a much more 'fantastical' direction compared to what I normally do.
A third option I often stick with is picking culturally specific names. I've got several families with Japanese names, e.g. Shigure and his daughters Yuriko, Akane, Sakura, or the Nagai family Jun (father) and Yumi, their son Shun and their daughter Kaho. There are tons of lovely girl names ending in -ho, such as Miho, Shiho, Maho, Chiho, or ending in -yo/yu (Miyo, Ayu, Mayu, Sachiyo, Chiyo, Sayu) etc.
So yeah, like others have said, it's best to choose names YOU like, possibly from people you know or that you have some sort of connection with.