This mono doesn't refer to mononucleosis--the infamous "kissing disease" that stirred such a buzz in the hallways of my junior high school. No, this is the much less racy monologophobia--the fear of using the same word more than once in close proximity.
Like most afflictions, monologophobia appears in varying degrees. Mild MLPs--hip talk for monologophobes--blanch at the repetition of a word within two or three consecutive sentences. Moderate MLPs will tolerate some repetition, as long as the words are spaced fairly far apart in a longer document. I once knew a hard-core MLP who wouldn't abide the repetition of certain words anywhere in the entire document.
So did you catch my sneak attack in that last paragraph? Repetition. Repetition. Repetition. There, I just KO'd a couple hard-core MLPs.
While I think it's best to keep your writing fresh and interesting by avoiding word repetition as much as possible, don't sacrifice clarity or a consistent writing style just to keep from using a word more than once. Don't make your "loud guy" in one sentence into a "vociferous male" in the next--unless you're intentionally going for a comic effect.
I run into the repetition dilemma a lot in my health care writing. One word that pops into my mind is surgery. While I sometimes use operation or procedure as a substitute for surgery, there are often times when surgery is simply the best word, no matter how much I've already used it. Procedure is a very broad term, and operation can be confusing--am I talking about the surgery itself or the operating of the business?
Sometimes you can minimize the sense of repetition by varying the sentence structure. If you started the last sentence with the repeated word, try constructing the next sentence so it appears in a different location. Or use it in another form--as an adjective instead of a noun, for instance. (Take a look at how I used sometimes in this paragraph and the last one.)
So my message to you is this: Don't worry too much about repeating a word if it is the best and clearest way to get your meaning across. Just say no to monologophobia.