Well, it really depends upon your needs. I have found that most published standards are much too complicated for the average user to comprehend and quite honestly cover much more ground than is required in most shops.
If the office has been operational for very long, there will be users that will have developed a certain drawing style utilising certain layers, linetypes, lineweights, etc. that work for the purpose. The biggest problem with getting users to adopt a set of standards is their complexity. No matter what, a standard will only cover most circumstances and there will always be a situation that isn't covered. The standard must be flexible enough to allow for this.
The real question you need to ask is not "What standards should we have?", but rather, "How will standards improve our productivity, accuracy, and subsequently, the bottom line profitability?" Once you have the answers to that question .. and answered the numerous other questions that will undoubtedly spawn, then you will have a good idea about what it is you need to have in your standards .. then you should find something that fits your needs specifically, barring that, develop your own from scratch. Beware though, developing a set of standards from scratch can be a time consuming and painful process.
It is also helpful to get input from the users ... how will a layer naming standard impact the users? Will it be easy to remember? Do you really need 27,000 layers? Do you need linewights? Can you plot with a CTB or would STB be better?
User interaction and flexibility will be key, and it is imperitive that the staff supports the standards, else compliance will bot happen, and policing them will become a full time job.
At my last employer, over the course of 10 years, we had developed a very complex yet very simple set of standards. The user didn't have to question most things ... after having a basic standard in place, within a few months we were able to implement creative programming solutions to assist the designers. These solutions further solidified the standard and soon, the users would find that compliance with the standards made their life simple, and unbearable if they did not. For example, we could automatically generate a roof section, size all beams, calculate supports, and label all pertinent details with the simple click of the mouse ... in 3 seconds ... however, if the user did not follow the drafting standards (layers, linetypes, colors, block names etc) the section would not generate properly ... creating one of these sections manually could take close to 2 hours. It was easy to guarantee compliance, if for no other reason than this.
In the end, your standards have to be workable for you, and so far, all of the standards I have found are essentially for offices that share with different organizations, where knowing one standard guarantees that you will be able to manipulate the incoming drawing. If you rarely share drawings and rarely use other's drawings, I wouldn't worry with using a published standard as long as you have one that can guarantee success within your organization.
As far as I can tell, BS, AIA, and ISO standards are much too complicated for most offices. Others may feel differently though.