This fellow wrote a column proposing a neat writing exercise. The premise is simple: Select at random two sentences from different books, and write a paragraph to bridge them. I've read two books suggesting similar calisthenics, Pocket Muse and The 3 A.M. Epiphany, and I think both are worthwhile.
You've got to be careful with etudes. Too much time spent playing Hanon and you'll end up sounding like a piano teacher. The trick is to get the patterns under your fingers without allowing the phrases to bleed into your voice. But a well-written etude is invaluable. It captures a lesson learned in the real world by veterans and makes it accessible to beginners. It can't substitute for experience, but it can fend off bumps and bruises.
I've always wanted to get a license to drive both a motorcycle and an 18-wheeler. I figure if I learn to drive everything on wheels, it will make me a better driver in my own car. The same principle applies in writing: There's almost no correlation between journalism and science-fiction, but practicing one will certainly impart skills to aid the other.
One writing exercise from The 3 A.M. Epiphany:
Let two characters reconstruct, on paper or in spoken words, a conversation after the fact, perhaps disagreeing over the words and the meanings of some of the words. There should be some kind of problem at the heart of this conversation, something troubling to both these characters, which causes them to fight over the very memory of words and the meaning of the alternate speeches remembered.I doubt I'll become a great novelist; and if I did, I wouldn't incorporate that scene. But it's an obvious challenge, and it would force me to confront specific problems as a writer -- devising plausibly different sentence structures, balancing consonance with dispute, and eventually reconciling contradictory ideas. I think a carpenter becomes better for having felled trees and fashioned rocking horses. I think writing the occasional bit of tricky nonsense must make a better writer.