A first step in any migration is to clean up your entry data. That doesn’t change when moving from WordPress to ImpressCMS.
Cleaning up your content can be done in several ways : removing old or no longer relevant posts (news items get old soon, and Google doesnt like stale news items), looking into content types that perhaps no longer need to be on the new site, and cleanng up your tags and menu structures.
It depends mainly on your content, so it is difficult to automate this step. However, if done correctly at the beginning of a migration, this step can make the difference between success and failure in the end.