One can attain a person's forwarding address by mailing a letter to the old address, by submitting a request to the U.S. Postal Service, by searching public records or by asking the person directly. Reverse lookup services also may provide an address to match a known phone number.
The standard method is to send a letter or other mailing to the old address and type or electronically print the words ?Return Service Requested? on the front of the envelope directly above the mailing address. This prompts the postal service to return the letter directly to the sender with a yellow sticker showing the forwarding address registered by the recipient.
Another option is to ask the USPS. Upon request, the USPS is authorized to disclose address information for any customer, unless the customer has specifically requested otherwise on his change of address form. In most cases, the USPS can disclose an address for use in legal proceedings.
Another method is looking for the person in public records, such as the White Pages. The caveat to this method is that the new address may not become public record for 30 days. If it has been more than a month since the person moved, this is the easiest and quickest way to obtain the forwarding address.