I'm working on a team that will be redesigning an internal website that's been live since the early 2000's. The design has not been updated in that time, only content. I'm wondering if there are any specific techniques that can be implemented into the research process to ensure that user flow is disrupted as little as possible when transitioning into the new site.
The new site will be completely redesigned in order to make it mobile-friendly and appease new users, though a large percentage of employees working at this company have been using this particular design since it's implementation. Specifically, I'm interested in learning particular techniques that can be implemented during the research and design process in order to keep flow disruption to a minimum for employees that are used to the current design.