Personally, when I am dealing with uv mapping in nifskope, I often have trouble figuring out where on the texture the triangles I am dealing with are located. This happens because some of the textures are have very little visible structure.

My solution to this was to make an image that tiles the texture surface like this:

upper left: dark
upper right: blue
lower left: green
lower right: red

And of course each tile is again subdivided in the same fashion.

So, now I can install this image as the texture I am dealing with and reload the nif to orient myself.

If you find this useful, or if you have better suggestions, let me know?

version 1.1 adds a texture with densely packed numbers on it

version 1.2 changes that numbering system so that the numbers are easier to find

Finally, if you are working with textures (or if you care about them), this is an excellent page of documentation on the DDS file format: http://www.hard-light.net/wiki/index.php/Herra_Tohtori's_texturing_tutorial -- and http://www.fsdeveloper.com/wiki/index.php?title=DXT_compression_explained is another.