Know whether you need UI, UX or both
Research, information architecture, user flows, wireframes and finished interface design are related but distinct forms of work.
Define the product context
Target users.
Primary user flows.
Existing product or greenfield build.
Required screens.
Design system status.
Mobile or desktop requirements.
Developer handoff expectations.
Look for relevant product work
A strong marketing-site portfolio does not automatically prove product-design experience.
Beautiful screens can still solve the wrong problem.Ask candidates to explain why their interfaces were structured the way they were.
Plan developer handoff
Agree on files, components, states, specifications and how design questions will be handled during implementation.