If you work with capable directors, the final decision regarding tempo is theirs. However, if your director wishes to establish the tempo, it must be communicated to you before (or as) you begin the introduction. This can be done if you are within seeing range: the director can tap or subtly direct a few measures for you.
You should practice with the director well before each service. As you do so, you will begin to learn each other's preferences, and to build a mutual trust. The need for the director to establish the tempo before the introduction may later diminish.