Ask Marketing Experts search engine marketing forum

[admin]

if you own multiple websites, its not a good idea to aggressively link between them. It is important to let the sites remain as autonomous as possible. Linking between a few relevant pages is fine, but its not a good idea to swap links on every page.

Deeplinking and keeping links varied is helpful, but keep links to a minimum.

[7thDsites]

It's also a very good idea to get some variance between IP addresses as well, i.e. if you have multiple sites get them, or some of them anyway, hosting with different hosts so you get some different IP addresses. You can also ask you host to give you a different IP that's not on the same Class C block as some of your other domains - they may charge you extra though.

It's also recommended that you vary your whois info so that all of your domains are not registered, admin'd, etc... by the same person or company. This can be done by simply using your domain name as the registant.
You do however need to keep your info as up to date as possible as if ICANN tries to contact you through your whois info and cannot they may take your domain name from you.

The above mentioned steps are more important now than previously as Google is now a registrar, no they're not selling domains, but they do now have easier access and abilities to cross reference domain ownership/whois registration info.