My shop writing guide included instruction to spell it out once, then list the acronym, and use the acronym (or initialism) afterwards. I don't know if it was something the Department of Defense (DoD), the United States Marine Corps (USMC), or something specific to how our customers wanted our product presented, but it seemed like a good system. You never have to leave the document you're reading to find out what an acronym stands for, and you still get most of the space savings.

Oh, and if you were going to use a term once, don't bother with the acronym at all (broken for illustrative purposes above).