A Voice from the Past - Gregory the Great

These are the things that a Bishop of souls should observe in the diversity of his preaching, that he may solicitously oppose suitable medicines to the diseases of his several hearers. But, whereas it is a matter of great anxiety, in exhorting individuals,  to be of service to them according to their individual needs, since it is a very difficult thing to instruct each person in what concerns himself, dealing out due consideration to each case, it is yet far more difficult to admonish innumerable hearers labouring under various passions at one and the same time with one common exhortation.

Gregory the Great, 540-604 AD, Pastoral Rule, Part II, XXXVI, (translated by Rev. James Barmby, Nicene and Post-Nicene Father, Philip Schaff and Henry Wace, T & T Clark and Wm. B. Eerdmans Publishing, 1997, Second Series, Vol XII, p. 69)

How should a sermon be framed to meet the needs of all the hearers? What pitfalls should be avoided?