Writing forces you to think better
I honestly don’t know what works for others. The act of writing, like any art, defies description. Some of the best advice I’ve seen regarding how to write essays is from Paul Graham. He says writing is thinking, and, insightfully, that writing forces you to think better. He wrote, “Just as inviting people over forces you to clean up your apartment, writing something that other people will read forces you to think well.”
My other suggestion (also, I think, stolen from Graham) is to concentrate on writing things with lasting value. I’m not sure I’ve been doing a good job of this at all lately — I think too much of what I write currently at DF is about stuff that’s only relevant right now. I’m certain that what helped me make a name for myself, what built the DF readership, were the long pieces I did in the first few years, most of which are still relevant, or at least still interesting.
There are a lot of people writing for the web today; but there aren’t that many at all who are trying to do great writing for the web.