If the package uses ./configure, add support for cross-compiling to debian/rules using --build and --host with values from dpkg-architecture. (Not CDBS.)

--build $(DEB_BUILD_GNU_TYPE)
--host $(DEB_HOST_GNU_TYPE)

-nodocs and -nocheck - Please add support via DEB_BUILD_OPTIONS and ./configure (if used). However, note that nodocs generally only drops -doc packages (which the emdebian patch files will do anyway). emdebian needs to drop changelogs, readme, news, copyright, info and man pages too. The advantage of supporting -nodocs is that the Emdebian build doesn't have to generate unused documentation. -nocheck is very important, if your package does not support skipping make check, it will complicate updating your package within Emdebian.

idempotent options - avoid trying to patch or clean a file that cannot be generated in a cross-build.

internal objects - if the package builds a program to do an internal task during the build, provide a way to do the task without executing compiled code or to avoid the task completely.