apt-get source <package name>

cd <in to source tree>

# (only cdbs .deb packages)
# This creates a temporary source directory for the new changes.
# and starts a sub shell. In this shell you make changes in the
# temporary directory and on exit it creates a diff/patch.
cdbs-edit-patch <patch name>

# update the change log and version number
dch -i

#build the package
# if you don't have a gpg key run:
debuild -us -uc

# else
debuild


# Done...

# Extra stuf
# .bashrc:
#   - add 'export DEBEMAIL="name@mailserver.dom"' for automatic correct
#     e-mail in change log
#
# .devscripts:
#   - add 'DEBUILD_DPKG_BUILDPACKAGE_OPTS="-i -ICVS -I.svn"' to
#     remove .CVS and .SVN directories
#   - add 'DEBSIGN_KEYID="1234567890abcdef"' for automatic signing
#     with corresponding key.