Mindmapping

Definition by Wikipedia

A mind map is a diagram used to represent words, ideas, tasks or other items linked to and arranged radially around a central key word or idea. It is used to generate, visualize, structure and classify ideas, and as an aid in study, organization, problem solving, decision making, and writing.
It is an image-centered diagram that represents semantic or other connections between portions of information. By presenting these connections in a radial, non-linear graphical manner, it encourages a brainstorming approach to any given organizational task, eliminating the hurdle of initially establishing an intrinsically appropriate or relevant conceptual framework to work within.
A mind map is similar to a semantic network or cognitive map but there are no formal restrictions on the kinds of links used. The elements are arranged intuitively according to the importance of the concepts and they are organized into groupings, branches, or areas. The uniform graphic formulation of the semantic structure of information on the method of gathering knowledge, may aid recall of existing memories.

In the real world
I’ve encountered several people using the technique during my career, and recently I’ve started adapting it also (for the colleges I’m attending at Wenk). In basics you’ll have to do the following (please not that I’m still a novice!):

Use just key words, or even images if it’s clearer for you.
Start from the center of the page and work out.
Make the center a clear and strong visual image that depicts the general theme of the map.
Create sub-centers for sub-themes.
Put key words on lines. This reinforces structure of notes.
Print rather than write in script. It makes them more readable and memorable. Lower case is more visually distinctive (and better remembered) than upper case.
Use color to depict themes, associations and to make things stand out.
Anything that stands out on the page will stand out in your mind.
Use arrows, icons or other visual aids to show links between different elements.
Don’t get stuck in one area. If you dry up in one area go to another branch.
Put ideas down as they occur, wherever they fit. Don’t judge or hold back.
Break boundaries. If you run out of space, don’t start a new sheet; paste more paper onto the map. (Break the 8×11 mentality.)
Be creative. Creativity aids memory.