One of the most common stylistic mistakes aspiring writers make is to rely too much on the verb "to be." "To be" is the most basic verb in the English language, and writers can all too easily find themselves using it in almost every sentence.
Unfortunately, "to be" happens to also be the weakest verb in the English language. To understand the truth of this assertion, ask yourself what you imagine when you hear the word "run," or "jump," or "scream." In each case, you probably got at least a flash of a mental image, of someone running, or jumping, or screaming. Possibly one or more of the words even evoked a memory or triggered a very vivid image. Now, ask yourself what you imagine when you hear the word "was." It doesn't give you any sort of mental image at all. It can't, because the word "was" alone provides no material around which an image or sound or smell or texture can coalesce. The word "was," like most of the forms of "to be" leaves the mind blank, a surefire way to bore the reader.
To see what a difference avoiding the use of "to be" can make in your writing, consider the following short paragraph:
As president of the debating society, my first duty was to schedule regular meetings and ensure that there were topics for us to debate. The topics were chosen from newspaper articles that were about controversial topics. Since it was a school club, I was forced to avoid topics involving religion and ethnicity.
In three sentences, the author has used forms of "to be" six times! You can practically feel yourself beginning to fall asleep as you read it. Now consider the following revision:
As president of my school's debating society, I scheduled regular meetings in which the club members gathered to discuss some of the most controversial issues of our times - abortion, euthanasia, the death penalty, and many more. Often, these topics were ripped from the headlines of local newspapers, though school policy prohibited me from referencing any issue involving either religion or ethnicity.
The revised version uses only one form of "to be," and that paired with "ripped," a much stronger and more compelling verb than "chosen," as in the original. Note that the revised version also includes more specificity than the original, by listing actual topics debated by the club members.
If you notice that your writing overuses forms of "to be," go through and ask yourself who or what is responsible for the things you are describing. So, in the case of the sample paragraph above, when I revised it, I asked myself who or what made me avoid topics involving religion and ethnicity. Well, it was school policy. Once I made school policy the subject of the sentence, "prohibited" emerged quite naturally as a strong verb, and allowed me to eliminate two instances of "was." Also, notice that often information introduced with a form of "to be" can be conveyed through the use of adjectives. So, for instance, in the sample paragraph, I eliminated "that were about controversial topics" merely by using the adjective "controversial" to describe the issues in the first sentence.
Sometimes, of course, you have to use forms of "to be." Most notably, the verb is a necessary part of the passive voice and the progressive tenses.
The passive voice turns the object of an action into the subject. So, the active voice sentence "I picked an apple" can be rewritten as "The apple was picked [by me]." Generally, you should avoid using the passive voice, with two exceptions:
1. The passive voice can come in handy if you do not know who undertook an action. So, in the above example, the phrase "The apple was picked" might be acceptable if you were writing about an apple and didn't know who had done the picking.
2. The passive voice also comes in useful for keeping focus on a particular subject. So, if I were writing a story about the apple, for instance, I might prefer to use "The apple was picked," in order to keep the focus on the apple by keeping it as the subject of the sentence.
The progressive tenses are vital for establishing time relationships. So,
"I was driving along chatting on my cell phone when a deer jumped out into the road in front of me."
The use of "was" in this sentence establishes that the driving was occurring at the time that the deer jumped out onto the road. Obviously, there is nothing wrong with the progressive tenses, and you should not go out of your way to avoid them.