Here enters spell check.
While this is by no means a substitute for proofreading or editing, it can save you time and energy by taking care of the "easy stuff"—for example, transposed letters in a word—so you can focus on the more complicated stuff—for example, "from" instead of "form" or convoluted sentences.
So my message today is simple: no matter how short your piece is, no matter how many times you've read through it, no matter who else you've gotten to critique it:
Always use spell check.
Make it the first thing you do before you start the editing process and the last thing you do before you click the Print or Send button.
You'll be amazed at what you missed.