Excerpt from 140 Characters: A Style Guide for the Short Form, page 18.
How many microscopic adjustments are made to a sculpture before it is complete? How many stitches go into a fine garment? This is the level of awareness you must achieve: down to the individual character.
Judge your simplicity by skimming your words.
Your readers will skim it. They will misunderstand it. They will even repost it, having skimmed it and misunderstood it. Expect this, plan for it, optimize for it.
Get ready to say it once. Or, get ready to say it wrong, delete and repost really quickly. If you’re lucky, no one will notice your mistake except the search engine. Limit yourself even further than the constraint requires, and then having the extra freedom will seem like a luxury.