Hey,
Form I-944 has quite a bit of supporting documents that go with it depending on your situation, be sure to read the instructions for this form carefully. Many people have gotten a RFE for this form so be sure to pay CLOSE attention when filing it out. When in doubt ask questions on the forums.
This should be updated with a strikehtrough through it since I-944 is not longer required.
Just a heads up as of 1/18/2024:
I sent an original copy of my birth certificate along with a photocopy of the birth certificate. I received them both back along with a copy of first page of the I-129f petition, a copy of the front of the envelope I sent it in, and a letter from the "SERVICE CENTER DIRECTOR" essentially stating that I didn't need to send the birth certificate and should wait until they ask for it if they decide it is necessary because it slows processing.