If you are new to packaging you should start with a package which is not
already packaged and also not a library. The only one of this type is
flintqs. This one does not have an upstream other than Sage, so you
should download it from
http://www.sagemath.org/packages/upstream/flintqs/
also take a look at the patches in the spkg from
http://www.sagemath.org/packages/standard/
It can be extracted with "tar -jxvf *.spkg"
The packaging should be done in the debian-science git.
I'll maybe not be able to answer questions next week, in that case just
ask this list.