Use a large piece of poster board. Start from the middle of the page so you can work out in all directions.
Use just keywords, or wherever possible, images.
Make the center a clear and strong visual image that depicts the general theme of the map. Create sub-centers for sub-themes.
Put keywords on lines. This reinforces the structure of notes.
Print rather than write in script.
Use color to depict themes and associations.
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.
If you run out of space, paste more paper onto the map.