There are many factors you should consider before attempting such a risky manipulation of the SERPs. You should have a firm grasp on things like having your sites on different class-C IP blocks, not interlinking all your sites to form a closed circle, using different anchor texts, adding the links over periods of time, not interlinking from the navigation menus, having external links to authority sites, etc.
If you ask a question on each of these aspects to 10 different SEOs, you will get 11 different responses. This is because not only is this not an exact science, but mileage varies from site to site. I believe Google will let some industry sites get away with what other industries, just like Google will not let a new site get away with what on old site can do.
Since this is a complex issue, I recommend you read as much as possible on the theme. Once you have a good theoretical foundation, THEN you can play with it. Donít go ahead and build 50 websites, take it little by little, build a few, experiment, donít interlink everything as to not put all your eggs in one basket of woven sites. There are many past threads here at webmaster world that could help:
Here you will find an old overview, but non the less valid:
Crosslinking, Interlinking and Reciprocal Linking: [webmasterworld.com...]
Not so on the topic yet a great read:
Safely Crosslinking Sites for Users: [webmasterworld.com...]
Interlinking of Related Sites: [webmasterworld.com...]
A more recent discussion
Interlinking Site Penalty?: [webmasterworld.com...]
Interlinking network of 300 sites good or bad?: [webmasterworld.com...]
And for more: [google.com...]
Best Luck to ya