I agree with most of what has been written here.
My two cents:
After you've gained the backing of management and you observed your power users in action so you know you won't be hindering their performance...
I know we didn't want to talk about specific disciplines but:
It depends on your business and company type.
Are you a company that produces wigets and sells them to outside sources, and so all your drawings and cad work remain internal?
If so, a nice basic easy to follow cad standard that meets your industry needs, that you create for your company should suffice.
Are you a company that designs buildings and construction projects for it's own clients, as well as consulting for other clients using other cad standards such as GSA, ACOE, VA, USCG, etc?
Well then it's in your best interest to streamline everything you can to the most common cad standards. For this type of business (atleast in the US) seems to be National Cad Standards (NCS) because most of these orgaizations use this as a basis for their standards.
With all that said, there are common standards that I feel everyone should be following, most of them mentioned already (and don't make it any more complicated then it needs to be):
File structure / File naming /layout naming (and procedures to be followed)
Layer names and mangagement (A layer for everything and everything on it's layer)
Named dimstyles and textstyles for your company standard (keep names genaric)
File Templates
Block Libraries
Basics:
All entities ByLayer: color, plotstyle, lineweight, and Linetypes
Block entities created on layer zero, (or block defined on layer zero if entities are on specific layers)
Common coordinates/insertion points for all files (blocks, title blocks, base plans etc.)
Ortho, Object Snaps, Accuracy.
I feel that my cad files and my printed drawings are my product.
My drawings should look good, be accurate and complete, easy to read and follow whatever the standard is, and my cad files should be set up in a way that someone can follow behind me and edit the drawing in my absence.
Everything sould make sense, clean cad work without extra garbage around in MS or PS if possible.
Have you ever gotten into someone's drawing to edit it and say WTF??
That is why standards and procedures are important!