You can use Customer Validation Rules in Company Settings to configure what pieces of information are required when creating a customer.
In the example above, the user has added "Email" and "Zip" to the list of required fields. Now attempting to create a customer without taking either will result in an error.
Any field that is set as required will show up on the General Tab as well as their subcategory.
Important: If you add a new required field, this will be applied for new customers AND will be required to update when saving a ticket for an existing customer.
Note: Creating a new customer will always require at minimum First/Last Name and Primary Phone Number.