A useful DFM conversation begins with the most current project information. The goal is not to delay a project; it is to identify the questions that should be resolved before production decisions are made.
Start with the available design package
Include Gerber data, BOM, CPL / pick & place, assembly drawing and the requirements you already have. If something is not ready, state that clearly so the review can be scoped appropriately.
Clarify production intent
Prototype, NPI and recurring production programs can require different planning. Define the current stage, expected quantity and any target timing that matters to the project.