Company Culture: Balancing Identity and Integration

I have been involved in numerous acquisitions over the past several years, and culture is unquestionably one of the most (if not the most) critical areas to focus on both pre- & post-merger. When an independent company becomes part of a larger organization, employees often struggle between maintaining their original identity and adopting new norms. What are the most effective strategies you have utilized for striking the right balance between cultural preservation and operational integration?