Gathering access.
FROM YOUR CURRENT HOST
Control panel access, or a full backup FTP or file access Database access
FROM YOUR REGISTRAR
Access to change nameservers
That is the one that stops migrations entirely if you do not have it.
WHAT TO ESTABLISH FIRST
Where the domain is registered Whether you can log in there Where DNS is currently managed
Those three determine whether the migration is straightforward or difficult.
WHAT TO RECORD
Every DNS record, including mail and verification records Your email accounts and which are in use Any cron jobs PHP version and any special configuration Which applications are installed
WHAT TO TAKE
A full backup from the current host, downloaded to your own machine.
Not left on the old server.
IF YOU CANNOT REACH THE REGISTRAR
Resolve that before anything else. Open a ticket and we will advise.