The 90 Seconds Rule--
In my previous blog I talked about how users can only stand being in Help (and away from the task they would rather be doing) for about 30 seconds. Nice, round number.
Another rule I find useful is the 90 seconds rule: Users will struggle on their own for at least 90 seconds before going to Help. So don't waste your 30 seconds on something the users will discover on their own in their 90 seconds.
For example, a product I work on has a table of firewall rules, and the user can change the order of the rules by selecting a rule and then clicking either an up or down arrow on the UI. Well, this is a fairly well-used and well-known convention to most software users. But even if it's brand new for some users who want to change the order of the rules, they will figure it out in their 90 seconds of fumbling. How long will a user sit there looking a rule that's too low in a list without saying, "Hmmm, I wonder if this up arrow does anything." So I spent my 30 seconds giving tips and guidelines about when a rule should be higher in the list and when it should be lower.
But what about the poor user who doesn't figure it out? I still documented it as a note in one of my tasks. I just didn't create a big procedure about "Changing the order of the firewall rules."
So another way to keep your Help files lean is to focus on information that the user will not be able to get from experimenting on the UI (which is exactly what they do before going to Help).