Each note card should include
a. full source information, notes from the source, and a page number where the information was found.
b. word-by-word quotations; summarizing can be done later.
c. notes from the source, an identification of the source, a page number where the information was found, and a label for the sub-topic.
d. one fact only, on one side of the card.

  C. Notes from the source, an identification of the source, a page number where the information was found, and a label for the sub-topic.

Explanation:

  Notecards are an important tool to gather information about the paper you are trying to write. These cards include the details needed for the bibliography. It is important to write down all the details needed because if not you´ll have more work to do.

  I hope this answer helps you.

The significance of the piece of velvet is that Lennie likes to stroke soft thing so his aunt Clara gave it to him so he would stop killing small animals by stroking them to hard.  
(its been a long time since I have read the book, hope this helps.)