Great point advidana. Also be wary of copying guide specs from equipment manufacturers without a thorough understanding of what it means.
I use CSI and have found the basic materials specs are a good starting point. The equipment specs are designed so they can be satisfied by wide range of manufacturers for bid jobs. If you want something different than run-of-the-mill products, you need to edit appropriately. As an example, for switchboards CSI is very vague. It covers standards compliance and that's about it. I use that as a base to develop my own specs to get what I really want. CSI's spec editing add-on's for word processors make it easy to edit and format.
As an engineer, the "weasle words" have saved my (client's) a** a time or two.
Writing good specs is an art form and a talent that many engineers lack. Too often once the drawings are done the project gets shipped with the engineer's off-the-shelf spec book that's been used on every job for the past ten years. When the junior engineers start turning out projects, they copy that same book, often little idea of it's contents.