Below is an ajax newsletter subscription example i put together. It displays a single input field form that once submitted emails the subscriber details to a specified recipient. This script can be used in many ways, you could even change the function to add the details directly to a database.
When moving a wordpress website from one server to another it is almost never necessary to do any database updates but when your moving your wordpress website and it is under a new domain name. The below query will come in handy as it allows you to find and replace any information in your database.