Use the active voice.

The active voice is usually more direct and vigorous than the passive:

I shall always remember my first visit to Boston.

This is much better than

My first visit to Boston will always be remembered by me.

The latter sentence is less direct, less bold, and less concise. If the writer tries to make it more concise by omitting "by me,"

My first visit to Boston will always be remembered,

it becomes indefinite: is it the writer, or some person undisclosed, or the world at large, that will always remember this visit?

This rule does not, of course, mean that the writer should entirely discard the passive voice, which is frequently convenient and sometimes necessary.

The dramatists of the Restoration are little esteemed to-day.

Modern readers have little esteem for the dramatists of the Restoration.

The first would be the right form in a paragraph on the dramatists of the Restoration; the second, in a paragraph on the tastes of modern readers. The need of making a particular word the subject of the sentence will often, as in these examples, determine which voice is to be used.

The habitual use of the active voice, however, makes for forcible writing. This is true not only in narrative principally concerned with action, but in writing of any kind. Many a tame sentence of description or exposition can be made lively and emphatic by substituting a transitive in the active voice for some such perfunctory expression as there is, or could be heard.

There were a great number of dead leaves lying on the ground.	Dead leaves covered the ground.
The sound of the falls could still be heard.	The sound of the falls still reached our ears.
The reason that he left college was that his health became impaired.	Failing health compelled him to leave college.
It was not long before he was very sorry that he had said what he had.	He soon repented his words.

As a rule, avoid making one passive depend directly upon another.

Gold was not allowed to be exported.	It was forbidden to export gold (The export of gold was prohibited).
He has been proved to have been seen entering the building.	It has been proved that he was seen to enter the building.

In both the examples above, before correction, the word properly related to the second passive is made the subject of the first.

A common fault is to use as the subject of a passive construction a noun which expresses the entire action, leaving to the verb no function beyond that of completing the sentence.

A survey of this region was made in 1900.	This region was surveyed in 1900.
Mobilization of the army was rapidly carried out.	The army was rapidly mobilized.
Confirmation of these reports cannot be obtained.	These reports cannot be confirmed.

Compare the sentence, "The export of gold was prohibited," in which the predicate "was prohibited" expresses something not implied in "export."