We had templates, a two-page packaging design guide and a lot of grey areas. As we did more work that deviated from the norm the inconsistencies started to pile up. Multiple hands on multiple files will do that unless you have clear guidelines to steer you through.
I combed over old logo guidelines, discussed with management, product managers and my fellow team members to gain some feedback. The logo guidelines we had were over ten years old while our two-page packaging design guide was six years old. By combing over (then current) print materials, template and website, we were able to make some decisions moving forward. In all, the whole process took about six months (off and on) to complete.
During the process, I realised that everything we needed was there (somewhere). Then it was just a matter of putting everything together in a concise communication piece that could be easily understood by anybody new coming into the marketing department. These graphic standards proved to be an essential tool for us. I can't imagine any in-house marketing department getting by without them and I often referred back to them weekly to keep my design and production focused on consistency.