Originally Posted by Colmike7

..You sure just getting backlinks to subdomains will get Sitelinks to show up?

First of all, Google doesn't tell what you need to get these, but these points help:

Get #1 for your main targeted KW
Have a high amount of organic search traffic (Not completely confirmed)
Make your site well structured and easy for spiders to navigate
High CTR
Popular internal pages
Well written and unique titles/descriptions
Use of Webmaster Tools


So basically, a clear hierarchy and contextual linking will help a lot more than backlinks alone to trigger Sitelinks.