30 Nov How to Serve a Court Order to Someone on the Internet
The above link can be used to find points of contact and addresses for Internet Service Providers in the US.
If you are trying to find someone on the Internet using common tools such as WhoIs Lookup, you will invariably end up with the name of an Internet Service Provider that holds the information. But, at some point you will need a court order to compel them to turn over records. Where to send the court order can be difficult to find. This link will give you all that is needed.