1.1 Split your window into a 3d view window and a UV/image editor window
1.2 Create a new image
a. With your cursor in the UV/image editor hit Alt-N or select Image*->New.
b. A dialog box will appear with settings. Usual settings are 512, 1024, 2048. The larger the image the more memory will be used by Blender.
c. You may need to select your new image by clicking on the up/down arrow and selecting "Untitled".
d. You may rename your untitled image by clicking on the text box and when it turns red or whatever color your theme is set to, just type in a new name. I renamed mine "UVnormap".
1.3. Unwrap your UV
a. In the 3d view window select your mesh (I have here a plane scaled up and subdivided twice)and go into edit mode by hitting tab-key if you are in object mode or select from the menu.
b. Press a-key to select all vertices/line/faces (the lines should turn yellow, and the faces pink).
c. Hit U-key or select Mesh->UV Unwrap in the 3d view menu. I just selected "Unwrap". The UV mapping will appear in the UV/Image editor window.
1.4 Export your UV
a. Move your cursor on the UV/Image editor window and click on UVs->Scripts->Save UV Face Layout... in the menu.
b. A dialog box will appear and you may need to change size. Here I used 1024 pixels. Then hit OK.
c. One of the windows will turn into a File browser window. Select your folder to save the targa file. Type the name of your file e.g. UVnormap. Then click Save UV (tga). You can also save it as SVG if you selected that in UV export dialog box.
That's the end of Step one. We will now temporarily leave blender and open Gimp to work on the UV map.