First, list all the nouns. Really -- all of them. You will get the most out of this if you actually go through these steps yourself as an exercise, and in doing so, I invite you to pick a paragraph from the document you want to index, or from any reference document you are familiar with. I suggest you take a blank sheet of paper, and write down the nouns in a column on the left side of sheet of paper. Leave plenty of vertical space between them for notes and additional data that you will add as you go along.
For our example paragraph above, the column of nouns looks like this:
water (used several times, but we only list it once)
