I write instructions for our assembly lines. Frequently, I need to call their attention to something that is not a step, but that they need to know. My usual way of doing this is to write, "Note: Do thus and so." This will be included with the steps, which are in a numbered list, although the note is indented and not numbered. Is my use of a colon here correct, or would another mark such as an em dash be more appropriate? Also, should the following word be upper- or lower-case? I would like to stagger them vertically, but I am limited on room.