1) to Contact the owner write to the email specified in the private whois data. Sometimes it email the private whois, which they manually send a letter to the owner of the domain, sometimes indicated by a special email, which is redirected to the mailbox of the owner. For example, so made Contact Privacy (Netfirms)
2) In some cases to contact the owner if you use the WHOIS of the Registrar. For example, who.godaddy.com will give some more detailed information about a domain registered with GoDaddy than any other WHOIS service.
3) There are services like 1stat.ru that store various information about the domains including their previous data WHOIS. Unfortunately, 1stat You will not do, because it collects statistics only on Russian domains, but similar services may exist for the rest of the Internet.