How do you create or select an icon for a feature?

How do you work out what icon type or image you need for a feature?

There’s been quite a lot of very small questions here in the form of “What is a good icon for feature X?”.

Instead we should be looking for a general guide in creating or brainstorming for an icon, that can be applied in a lot of situations and applications.

This could possibly be done by looking an intermediary step:

Feature / Semantics

  1. Terms that represent this feature
  2. Icon for that term

E.g.

Level of anger for client

  1. heat map
  2. Icon for heat map

This question is about step 1, the step you use to create a list, ideas or resource for possible icons that will be applied to the feature.