Although using the plural they for a singular antecedent is gaining acceptance, it remains a problem for localizers and for non-native English speakers. Whenever possible, you should write around this problem.

Microsoft style

A user with the appropriate rights can set other users’ passwords.

Authentication verifies the identity of the user.

Right-click the name of the person you want to call, click Make a Phone Call, and then choose from the list of published numbers.

Not Microsoft style

If the user has the appropriate rights, he can set other users’ passwords.

Authentication verifies that a user is who she claims to be.

Right-click the name of the person you want to call, click Make a Phone Call, and then choose from the numbers they have published.

If you cannot write around the problem, do not alternate between masculine and feminine pronouns to refer to the same individual, and do not use he/she or s/he. Using the slash mark in this way is confusing for non-native English speakers, and even many native English speakers consider it confusing and annoying.

It is all right to use he or she occasionally, but doing so excessively may distract the user. If you need to make third-person references to more than one person in the same topic, use he for some individuals and she for others. In all cases, leave no doubt about the antecedent for each pronoun.