Bring the spouse's own citizenship documents, education and professional credentials, and a description of the type of work being considered, whether a specific offer, remote work, or general interest. This lets counsel assess which route, if any, might apply to the spouse specifically.
Build the spouse's file separately from the principal's
Keep the spouse's documents organized as their own case: passport, resume, credentials, and any existing US immigration history. Don't assume the principal's employer letter or TN evidence has any bearing on the spouse's own eligibility. If a specific job offer exists for the spouse, its details, employer, duties, and timing matter just as much as they would for the principal applicant.
Hypothetical example: a spouse who is a dietitian assumes her professional background is irrelevant because she will be accompanying rather than transferring. It is highly relevant, since her own qualification may open a route of its own, and that possibility cannot be assessed from documents nobody has gathered. A first review would ask for her passport, degree and transcript, any professional registration, and a description of the work she would want, and would treat those as a case file in her name.
Where a specific offer exists, its employer, duties and timing matter exactly as they would for a principal applicant.