What's your naming philosophy?

Do you tend to prefer names that are "timeless" or trendy? Do you only look at top 100 lists? What are your criteria for the perfect name?
We're struggling hard with a name for this little boy. Our first son is Spencer, which is in the 300 range - our criteria were that when we say the name, people can understand immediately, and can spell it. We also liked that it wasn't super common.
DH is stuck on Callum for this boy, but I'm afraid that when it's said out loud, people will be like...what? Kevin? Colin? Calvin?
What's your philosophy on the best kind of name?