The whole category in one page.
THE TWO PLACES
Nameservers are set at your registrar. Records are held wherever those nameservers point.
Changing records in the wrong place is the most common DNS mistake.
THE RECORDS THAT MATTER
A, for where the website is MX, for where mail goes TXT, for SPF, DKIM, DMARC and verification
Everything else is situational.
BEFORE ANY CHANGE
Record the existing zone Lower TTLs a day in advance Know what must not change
AFTER ANY CHANGE
Query your authoritative nameservers directly to confirm Test the website and mail both directions Check every subdomain
WHEN MAIL STOPS
MX records missing, the mail hostname not resolving, or the cPanel routing setting wrong.
Those three account for nearly every case.
WHEN NOTHING RESOLVES
Domain expired, nameservers wrong, or no A record.
BACKING UP
Export your zone. No hosting backup includes DNS held elsewhere.
THE DIAGNOSTIC THAT SETTLES MOST QUESTIONS
Query the authoritative nameservers. It distinguishes "wrong" from "waiting".