DailyWritingTips has an interesting (interactive even) post on editing. Granted there are fancy spellcheckers out there, manual proofreading catches more than just misspelled words; you may find an inferior word that doesn’t really capture what meaning you want to convey, wrongly used punctuation marks, and most importantly, you polish your writing so it’s easily digestable.
Here’s a great tip left by a fellow commentor:
Here’s a tip I used in graduate school and one I pass along to my students: Read aloud to yourself.
When you proofread silently, you really tend to skim and possibly miss mistakes. But, if you read aloud, there is absolutely no way your mouth can keep up with your brain. Therefore, you have to slow down and you can “hear” your mistakes more easily.
People may give you funny looks, but not when grades come out and you are on top.
And don’t just edit words, edit content. Take out gratuitious, unnecessary thoughts and ramblings that are meaningless. Make your literary product concise. Copyblogger has a great post on how to tighten up your writing. Your blog is in constant competition not only against other blogs but against broadcast news websites, commercial retailers, IM conversations, emails and so on. By the time readers enter your store, the last thing they want to read is dense literature.