A couple of us at my current company are trying to move from the ad-hoc approach to a more formalised one. It sounds similar to the challenges you are facing.
A couple of articles by Neilson may help: Corporate Usability Maturity: Stages 1-4 and Corporate Usability Maturity: Stages 5-8. They provide a good overall background, and something to aim for.
The one element that seems to be working well for us is that we are weaving the UX Methods, timings and deliverables into our current project lifecycle. This has a few advantages of getting most people to understand the process quickly. The idea is we’ll be in the room when the project is just the germ of a ‘good idea’.
For deliverables, we are using some of the excellent templates available in the community, and have created a diagram that documents the UX Methods, UX Deliverables, and People Involved at every stage of our project lifecycle. We have also detailed what current products the UX stuff gets inserted into. This got people on board very quickly, as they can see the alignment — we didn’t want to give the impression we were re-inventing their wheel.
Another trick was to get UX as a principle in our Enterprise Architecture — it means that it has to be considered before any project gets sign off.
One final thought is engagement with stakeholders. I’m unsure what size your company is, but you’ll need to speak to as many people as possible, and get as many challenges to help refine and test your ideas. We’ve spoken to Solution Architects, Business Analysts, Testers, Project Managers, Department heads…etc…etc…etc. Get them on board as soon as possible.
Of course, each company will be different, so some of this may not apply. Good luck!