Download the package and try to build it:

PKG_NAME="package_name"; PKG_VERSION="version_number"; PKG_REVISION="revision_number"
mkdir ${PKG_NAME}; cd ${PKG_NAME}
apt-get source ${PKG_NAME}
sudo cowbuilder --build ${PKG_NAME}_${PKG_VERSION}-${PKG_REVISION}.dsc

If it is not a FTBFS, try to reproduce the bug. If it is a FTBFS, you have reproduced the bug while building.

cd ${PKG_NAME}-${PKG_VERSION}
dch -n

Fix the bug.

PKG_NMU_REVISION="nmu_revision_number"
cd ..
dpkg-source -b ${PKG_NAME}-${PKG_VERSION}
sudo cowbuilder --build ${PKG_NAME}_${PKG_VERSION}-${PKG_NMU_REVISION}.dsc

Check if new package works as expected. If it doesn't work, fix it, recreate the source package and rebuild it again until it works properly.

If it works run tools like debdiff and lintian:

PBUILDERRESULT="pbuilder_results_dirname"
debdiff ${PKG_NAME}_${PKG_VERSION}-${PKG_REVISION}.dsc $PBUILDERRESULT/${PKG_NAME}_${PKG_VERSION}-${PKG_NMU_REVISION}.dsc
lintian -F $PBUILDERRESULT/${PKG_NAME}_${PKG_VERSION}-${PKG_NMU_REVISION}*.changes

Sign and upload the package and send an email to BTS with nmudiff

debsign $PBUILDERRESULT/${PKG_NAME}_${PKG_VERSION}-${PKG_NMU_REVISION}*.changes
dput -e 5 $PBUILDERRESULT/${PKG_NAME}_${PKG_VERSION}-${PKG_NMU_REVISION}*.changes
cd ${PKG_NAME}-${PKG_VERSION}
nmudiff --delay=5

Workflows that inspired this one:

• gregoa's workflow: http://info.comodo.priv.at/blog/articles/rcbw/
• zack's workflow: http://upsilon.cc/~zack/hacking/debian/rcbw/