How do you pronounce Cerberus?

Contemporary pronunciation is with a soft c (as in 'cite') vocalized as an S, so it sounds like 'ser-ber-uss'.

However the correct Greek (and Roman) pronunciation would have been with a hard c (sounds like a K) therefore it should be 'Ker-ber-uss'.

Use the soft c if you want to sound like the majority of English speakers, use the hard c if you want to be more authentic.