I've created packages previously by using a Makefile, the command "dh_make --createorig", then adjusting files in the debian folder generated and finally using the debuild command to generate the .deb. That workflow is simple and works for me, but I was told to adjust it a little in a way that you could build the project from the sources without requiring the orig files and I'm unsure how to do it, but according to this (https://askubuntu.com/questions/17508/how-to-have-debian-packaging-generate-two-packages-given-an-upstream-source-arch) and this structure (http://bazaar.launchpad.net/~andrewsomething/imagination/debian/files) there must be a way. In my case I would have a folder with the sources and all of that and then a debian folder (generated with dh_make) but I'm unsure on how to avoid the debuild command to ask for the .orig files or if I should be using some other command for this.
Sorry for the superlong question, I think I provided all the relevant information, but I can clarify if anything is fuzzy.
If you want to create a Debian directory directly in the source package (ie you're packaging your own work, rather than from an upstream release) you could use the --native option to dh_make