When moving to Lightning Experience, it's important to factor in the human aspect of change. Use the Lightning Experience Change Management Hub for best practices, resources, and a guided path to preparing your users for the new experience.
Start small and test as you go using a phased approach.
Activate your entire org all at the same time.
Retire your legacy system and start fresh.
Learn how we rolled out Lightning Experience across all of Salesforce and the best practices we used in this free e-book.