Hybrid Migration and SharePoint upgradation

Hi,

We have a highly customized SharePoint 2010 application, now we have to Migrate content from another highly Customized SharePoint 2007 application (both the customizations 2010 instance and 2007 instance are different). The content from SharePoint 2007 application needs to be migrated to the instance on SharePoint 2010. Appreciate if someone could post any best guidelines for a smooth Migration process.

Best Regards, Paramesh.