Here is a run down on ways DV, OV, and EV certificates are validated by the certificate authority:
Domain Validation (DV): These certificates can be validated in minutes. The domain/website owner will submit the Certificate Signing Request (CSR), which triggers an approval email. Once approved by the owner, the certificate files will be emailed. If the user does not have access to the authoritative domain email you can opt for DNS Validation.
Organization Validation (OV): This certificate type takes a little longer to be issued because, you guessed it, your organization needs to be verified by the certificate authority (CA). The CA will check that the organization is registered and active, and that the address and phone number of the organization are valid (authentication call). The sources they may use for verification include government registries or through well known public directories like Yellow Pages and Google Maps.
Extended Validation (EV): These certificates can take a couple of days to validate as the process is more in-depth. The CA will verify it more or less the same way as OV certificates, however, there will be more checks to verify details with the organization (such as the registration numbers, the period it has been active, etc).