How do you decide which lead gets called first?

Question for founders, sales teams, and agencies:

When 20 new leads come in from different sources — ads, forms, LinkedIn, referrals, cold email — how do you decide who gets contacted first?

Do you use:

- lead score?
- source?
- job title?
- company size?
- form answers?
- first come, first served?
- sales rep judgment?

I’m curious because many teams say they have a lead generation problem, but the real issue may be lead prioritization.