Typically, and this is just what I have seen throughout several organizations, I don't think standards are specific about this, is that you only have one "hard" callout. In other words, you balloon the item once in one view and all the rest are reference. Whether or not you use a balloon with "REF" with it or you just use a leadered callout, you have only one balloon. The REF is for calling out the SAME component in a different view.
When the same component, such as bolts, screws, nuts, washers, and even manufactured components, are used in several locations in the same view and you want to balloon each one, then you prefix the balloon with the quantity that appears in the area (1X, 2X, 8X, etc.) The area is a general vicinity of your balloon that is obvious to the reader of the print so they can easily count how many you are referencing. When doing this, you must make sure that you balloon the same number of items in the drawing view as the quantity listed in your parts list. Any balloons outside of this view follow the recommendation above and you REF them.
--Scott
For some pleasure reading, try FAQ731-376
