I sometimes joke that I must be adopted because my parents have no aptitude for computers. I could make a similar joke about writing. Many of my immediate family, despite decent educations, seem to be incapable of writing a simple English sentence, much less a coherent paragraph.

One relative writes emails that are bereft of punc­tu­a­tion: neither a comma nor a full stop (period) is to be found. Capital letters occur, but too randomly for my liking. And everything is linked into one paragraph, no matter how long or disjointed. Yet, I’ve received adequately punctuated hand­writ­ten letters and postcards from him. I attribute his email sloven­li­ness to a com­bi­na­tion of laziness and hunt-and-peck typing. Whatever the cause, it reflects poorly on him.

John Scalzi has some Writing Tips for Non-Writers Who Don’t Want to Work at Writing. Here’s the summary:

0. Speak what you write … If what you’re writing is hard to speak, what makes you think it’s going to be easy to read? It won’t be. …
1. Punctuate, damn you: For God’s sake, is it really so hard to know where to put a comma? …
2. With sentences, shorter is better than longer.
3. Learn to friggin’ spell.
4. Don’t use words you don’t really know.
5. Grammar matters, but not as much as anal grammar Nazis think it does.
6. Front-load your point.
7. Try to write well every single time you write.
8. Read people who write well.
9. When in doubt, simplify.
10. Speak what you write.

Go read the whole thing.

I found some useful links in the comments that follow Scalzi’s Tips:

• One Simple Rules: Use the Active Voice
• Commas, Commas, and More Commas, for when you’ve mastered the preceding rules.

And here’s a few tips of my own:

• One thought per paragraph. Run-on paragraphs offend me and annoy me. If a paragraph has more than four sentences, it’s probably too long.
• Pick up something that was written by a competent writer who you enjoy and analyze a page. Why did they choose to break sentences where they did? Why are the commas placed where they are? Do the paragraph breaks make sense? What about the word choice? Did it clearly and succinctly convey their ideas, their tone? (Hell, just analyze this post.)
• Think before you write. Before you dive in headlong, what is it you’re trying to convey? This doesn’t have to take you very long. A few seconds before a short email is enough.
• Reread what you wrote, before you send it off. Revising mistakes is so easy on a computer that you have no excuse for not bothering.

This isn’t enough to turn you into a pro­fes­sion­al writer, but it will make a marked im­prove­ment in what you write.