Choose specific, descriptive words when you are making any statement on the GRE. Vague language weakens your writing because it forces the reader to guess what you mean instead of concentrating fully on your ideas and style.
WEAK: Mr. Brown is highly educated.
FORCEFUL: Mr. Brown has a master’s degree in business administration.
WEAK: She is a great communicator.
FORCEFUL: She speaks persuasively.
Notice that sometimes to be more specific and concrete, you will have to use more words than you may otherwise with vague language (as in the first example). This principle is not in conflict with the general objective of writing concisely. Being concise may mean eliminating unnecessary words. Avoiding vagueness may mean adding necessary words to illustrate your point.
Edit these sentences by reducing the vague language:
Drill #1. The principal told John that he should not even think about coming back to school until he changed his ways.