An old UX mantra is to test early and test often. Testing can take many forms, but by asking users, stakeholders and even staff members about their experience with the existing system - you are getting valuable information on the product and/or solution. Testing a proposed solution can include a high-fidelity prototype, microsite, screenshots, email surveys, stakeholder interviews, click through wireframes, and much more.
Tools: Sketch, Figma, Illustrator, Axure, Invision, HTML, Whiteboarding, Mockups, Usertesting.com