Brainstorming: We write in a paper everything that comes to our minds refering to the topic we are going to talk about. It is like many ideas raining from our minds to the paper if the ideas are good or not.
Making a list: We can also make a list doing sentences with words that are connected with the topic.
Freewriting: With this method we write whatever comes into our head about our topic, without stopping.
Mapping: Make a map with the topic in the middle and creating ideas in circles around it. This method give you lots of ideas that you can use in your essay.
For me the best method of organiced your ideas in order to write is mapping. It is a good way of think about new ideas and what are you going to talk in the essay.