Burke wanted this method to be  rigorous while still "allowing for the experimental range required by the subtle and complex nature of the subject matter," so these rules are more like guidelines which you can adapt to what your research requires. You start by noting concordances of words appearing together.  After a while of doing this, you will notice that some terms have many words clustering around them, like hubs in a network. Such words are key terms which you can start to focus in on. After a while, you will have built up a registry of concordances  which begin to reveal a structure.  You will notice that different things are being used as synonyms than what you would see for those words in a dictionary.

Now, look at one of your clusters where one term has gathered a lot of other terms around it. Start, as well as you can, to organize them from lower to higher order. Greater abstraction often means that it is higher up, but also look for how different terms are weighed up against each other in the text. What is clearly socially superior or socially inferior? What things serve as lower means to higher ends? What are the lesser categories and what are the higher categories?

Here is my methodology for conducting the indexing of Truman's speech:

1. I chose atomic bomb as a key term (since the speech is about the first nuclear bombing in world history).

2. I noted all terms directly referring to the atomic bomb and its development.  This became my cluster.

3. As I looked at the most concrete terms I saw they were all tools or means, so the natural step up is "what are they means for or a  part of?"

4. The words describing the effort all hint at a greater goal than themselves,  what is this greater goal? was the next logical step.

5. At this level,  it became hard to clarify which should be the God-term. The frequency of "power" seemed to hint  towards it. The God-term also needs to be self-causing and an end in itself. "Achievement" does not fit that, but "power "does.