The below may be outdated:
cvs -z3 -d:pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot co -r MOZILLA_1_8_0_BRANCH mozilla/browser/locales mozilla/dom/locales mozilla/extensions/reporter/locales mozilla/netwerk/locales mozilla/other-licenses/branding/firefox/locales mozilla/security/manager/locales mozilla/toolkit/locales mozilla/browser/config mozilla/client.mk mozilla/browser/config/mozconfig mozilla/browser/config/version.txt mozilla/build/unix/modules.mk mozilla/build/unix/uniq.pl mozilla/mail/config/version.txt mozilla/configure mozilla/configure.in mozilla/allmakefiles.sh mozilla/build mozilla/config
make -f client.mk configure
Checkout
cvs -z3 -d:pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot co -r MOZILLA_1_8_0_BRANCH mozilla/client.mk
Download
Apply patch (go to mozilla dir and...)
patch -i .../path/to/patch-file
(in this case the patch-file is l10n-checkout.patch)
Checkout
MOZ_CO_PROJECT=browser make -f client.mk l10n-checkout
Create a .mozconfig file in the mozilla directory (also look at: http://developer.mozilla.org/en/docs/Configuring_Build_Options)
. $topsrcdir/browser/config/mozconfig mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/../ku ac_add_options --disable-compile-environment
Make
make -f client.mk configure