Link building concept (Croslink different mediums sites for seo purposes)

[nikosvasilakos]

Hello all. This is my first post to seomoz.
A large News Media Group has a News Vortal and 3 magazines (for kids,health,fashion)
All those different mediums have their content in independant websites (since the branding of all 5 Medium is very strong).
My question is how to croslink them editorially for seo purposes?
Is it ok if i put a news box at every magazine site?
Should i create links to news articles or to news categories or both?
Do links from unrelated sites dilute your rankings for your key phrases ?

Thanks in advance