Assemble it as documents are produced rather than afterwards. Requesting copies from an employer or recruiter becomes harder once the hiring team moves on, and files held by third parties are not always retained as long as the applicant will need them.
Collect at each step, not at the end
Ask for a copy at the moment each document is signed or sent, while the person who produced it is still involved. After entry, add the admission record promptly and check it against what was intended. Set a reminder before any expiry date to review the set, confirm what will need updating, and identify anything that must be re-obtained in advance.
Ask the operating company to record a start date that follows admission or the effective date of status, and to hold off on assigning substantive work before then. Missing a scheduled appointment can affect the case, and an unexplained absence is harder to resolve than a request made in advance. Plan around the admission period actually granted rather than around the length of the project, and plan the extension before you need it. For a Canadian citizen with complete documents, the port of entry usually gives the fastest decision.