Create .deb package from source

First download or build source package. If it is compressed, extract it. Then open terminal and go to source folder, by typing

cd source_folder  (if it is in home folder)
otherwise,
cd /folder1/folder2/sourcefolder

For example, if you want to install gedit from source, and source folder of gedit in Downloads folder, then type :

cd Downloads/gedit

then type

dpkg-buildpackage -rfakeroot -us -uc

Note : You need to install dpkg-buildpackage and fakeroot first.
Open terminal and type :
sudo apt-get install dpkg-buildpackage && fakeroot