Use active voice as much as possible. If you don’t know what that means, “The boy threw the ball” is active voice. “The ball was thrown by the boy” is passive voice. Who is performing the action versus what or who is receiving the action?
Not that active voice also eliminates a preposition. The sentence is more clear and there are less unnecessary words. Tighter writing is better writing.
Use active voice as much as possible. “The boy threw the ball”, not “The ball was thrown by the boy.” Note it also eliminates a preposition. This is another way that tighter writing is better writing. There are exceptions, but use them consciously. For example, a statement such as “The board approved the new proposal” is often simply stated “The new proposal was approved.” Watch for needing a prepositional phrase following the verb, in which case you may be slipping into passive voice.
Marcha's Two-Cents Worth 