When I write to a "describe yourself" type prompt, I find myself wildly overusing "I am ..." type sentences. What are good ways to vary prose in this situation? (Preferably with examples)
The problem with repeated "I am... " sentences isn't that you're not varying your sentence structure, it's that you're not communicating the underlying meaning with your reader.
Consider the standard Essay format:
By itself, each "I am..." statement is an introduction to a fact. If you don't elaborate on that statement, the attribute you're trying to describe is meaningless.
For instance: "I am directionally challenged."
Okay, so what? How has this changed me as a person? Why should the reader care? Is it merely a descriptor, like my eye color, or is it more than that?
"When I get off an elevator, I always pause, taking in my surroundings and trying to determine if I need to turn left or right. Even when I get off the elevator at my workplace, the same one I've ridden 10+ times a week for five years. It doesn't bother me, and I'm not embarrassed by the fact. However, if I'm travelling with coworkers, I will choose to walk behind them. This is not because I feel lesser, or subordinate- it's simply more efficient. I will hold my own during any technical discussion, argue with my boss and his boss with no fear of retribution. But if I'm navigating to a new destination, even with GPS directions barked from my phone, I take it as a given that I will have to pull at least one U-Turn."
It's fine to start with the "I am" statement. After you start elaborating on what it means to you and the people around you, giving the readers the body and conclusion to support this introduction, you can revisit this statement and change it into something more.
"People sometimes underestimate me, when they see my hesitation upon entering a room. What they fail to realize is that I am not weak, I am not scared; I am just directionally challenged."