Custom customer fields can be a little daunting to implement, due to the fact that each customer is a collection of integrated sections. However if this is a step that needs to be taken, well here is the process that I have followed, helped by many online tutorials.
Administrator -> Customers -> Manage Customers
Select a customer from the grid.
On the left hand side there will be a section Customer Information, select Addresses. The Edit Customer’s Address will not be viewing the new customer fields and this will be visible by making entries into customer_eav_attribute for each of the custom fields to be inserted.
Example DB entry:
INSERT INTO `
Once this entry has been made it should be possible to see the values in the form. However it will probably be necessary to change the DB sort order for the new custom fields to position them on the form.