The list was provided by our HR for me.
copy of your H1B Application Packet
copy of your H1B Approval Notice----if you have two or more (eg. you ever extended your H1B, you should copy all of them, and, most important, notarize them by your HR).
Copy of your Passport/Visa
copies of 3 most recent pay statements (or original copies)
Employment Letter ---- this will be provided by your HR
Marriage Certificate, Birth Certificates (for all dependents) and valid passports