Typically, should refers to a recommendation or an ideal state. In technical writing, should is vague and is rarely helpful to users. Where possible, rewrite sentences in the imperative. Only use must to emphasize that the user has no choice but to follow a specific course of action.
Preferred
Discouraged
To help callers understand the options, record instructions as part of your personal greeting.
To help callers understand the options, you should record instructions as part of the personal greeting.
To help callers understand the options, you must record instructions as part of the personal greeting.
