How to document LabVIEW program?

Question

Is there any guidance for how to document a LabVIEW
program?

Answer 1

The LabView Style Guide has a chapter on documentation. Click here.
Here are some of the things I try to do on every VI.
Create VI Help info: on the VI's File menu, select VI Properties >> Category >> Documentation, then add you help info into the VI Description. That's what will be shown when the user shows the context help (Ctrl-H).
Front Panel:
Create help info for each control: right-click on the control, then select Description and Tip. The Description will be shown when the user shows the context help. The Tip will be shown (as a Tool Tip) when the user moves the mouse pointer over the control, even if context help is not shown.
Make control Labels descriptive. Numeric, Numeric 2, Boolean, etc. are not descriptive enough to be helpful to the user.
Use the control captions if needed.
Use the text tool to add free labels to the front panel if needed.
Diagram:
Show the label for each structure (while loop, for loop, case, sequence, etc.). Not just a free label: right-click on the border of the structure and select Visible Items >> Label. This way the label is attached to the structure and will move with the structure as you're editing the diagram. Make the label descriptive. For loops, summarize what you're doing. For while loop, state when the loop will stop. For For loops, if auto-index is used, state which input will set the number of loops. For cases, describe the criteria for selecting a case.
Within a case or sequence structure, use the text tool to add a free label inside each case or sequence frame to summarize what happens there.
Show labels for all control terminals. Some controls may not have their labels displayed on the front panel (e.g. buttons with their boolean text shown), but always display the label on the diagram.
Liberally use free labels to add more comments.
VI History:
Use it! On any VI window, from the Tools menu (the tools palette), select Options, the select Revision History from the pull-down listbox. Select Prompt for comment when VI is saved. Whenever the VI is saved, add a brief but meaningful comment about what was changed. This history is available under the VI Properties >> Category >> Revision History >> Show Current Revision History (or by pressing Ctrl-Y). It can be very helpful in debugging a program that stopped working after you made a bunch of changes.
Icons:
Create helpful (not just artistic) icons. I typically just use text to show an abbreviated VI name. Graphical icons can be helpful if it's clear to the user what the graphics mean. But I like text. I put my creativity into the program, not into a tiny picture trying to describe the VIs function to the user.
I'm glad you asked the question. The more work you put into your documentation now, the easier it will be for you or anyone else to use and maintain your programs.