I never wrote a loader, but I use lots of them. I think this would be a good way to start writing loaders.
You can first go and look at the source for the loaders. Most of the loaders are open source.
Here is a list of loaders:
http://www.j3d.org/utilities/loaders.html
Then you will have to get the format for the file. POV
Here is a place that explains the POV file format:
http://www.cica.indiana.edu/graphics/object_specs/POV.format.txt