What is the correct way to modify/patch a .spec file?

What is the correct way to modify/patch a .spec file? I need to add phonon-devel as a build dependency for python-qt4 so that I can run openLP. I do this by adding “BuildRequires: phonon-devel” to the spec file. Right now I just edited the .spec file on the OBS website. Will that stick or will it get wiped out the next time python-qt4 is updated? Do I have to use a patch file instead or is my method adequate?

You don’t need to patch the spec… Just add the BuildRequires and save. It remains there until you change it again. Patches should only be used as a last resort to fix stuff over the pristine source, for example critical bug fixes, packaging fixes…