Active Voice v. Passive Voice

Always use active voice.

The formula to construct is: S + V + O.
Meaning you start with the subject then the verb then the object (if there is any).

Berto kills the dog.
The subject here is berto, the verb is kills and the object is a dog.

If it is a passive voice it would be:
The dog was killed by Berto.
The action is performed on the subject.

Remeber this if there is "by" in the sentence it means it is on passive voice mode.
You always ask by whom if it is in the end or unknown it is probably passive.

Exemption to the rule is:

1. The subject is unknown.
2. The subject is irrelevant.
3. You want to be vague about the subject.
4. You want emphasis on the object.