Employment records covering the qualifying period abroad, organisational charts for both entities, ownership and incorporation documents, the proposed position description, and any prior US immigration filings or admissions. Evidence of the receiving entity's activity helps. A short written chronology saves more time than a large unsorted file.
Bring the boring documents, not the polished ones
The persuasive material is usually mundane: payroll summaries, signed appointment letters, minutes recording an appointment, and charts prepared at the time rather than for this purpose. Flag anything that may need translation and let the reviewer decide what actually requires it. Where a record cannot be produced, say so early and describe what exists instead, because a gap explained at the start is easier to work around than one found late.
It is worth explaining to whoever gathers the material why the unglamorous documents matter more. A chart drawn last week to illustrate a transfer was created for this purpose and will be read accordingly; a chart circulated to staff two years ago was not, and is therefore harder to discount. The same logic applies to appointment letters, minutes and payroll registers.
Ask the business to search for what already exists before commissioning anything new, and where something genuinely has to be created now, date it honestly and let counsel decide how it is characterised.