Something I see time and time again when observing technical support in action. Don’t ever assume that because you know where a certain feature resides in a certain application that the customer will also know what you’re referring to. If for example the location where you need a customer to modify a setting is at “Edit -> Preferences -> Options -> Formatting, in the desktop variant of application ‘x’, then that is precisely what you must communicate to her. Not, “go to the the formatting settings in application ‘x’, without any indication of what edition of the software you’re referring to.
And not just customers either – it’s a rule that should be adhered to just as rigorously when communicating with colleagues, no matter what their technical level.