Roger Ebert, back in 2010:
My rules for Twittering are few: I tweet in basic English. I avoid abbreviations and ChatSpell. I go for complete sentences. I try to make my links worth a click. I am not above snark, no matter what I may have written in the past. I tweet my interests, including science and politics, as well as the movies. I try to keep links to stuff on my own site down to around 5 or 10%. I try to think twice before posting.
Via Daring Fireball