There is a distinction between a conversational tone and sloppy writing. It’s comparable to “business casual” versus “for heaven’s sake, put some pants on!”
When talkin’ to a bud, ya gonna be droppin’ your g’s offa words, but do you really want that sort of thing in your writing, which represents to the world your competence, your expertise, your perceived intelligence?
Sloppiness reflects badly on you and on your brand, so avoid these common slovenly habits:
This is not pinkeye, but it does make me see red. “It’s OK to start a sentence with a conjunction.” Yes, occasionally this is fine, but it’s become an epidemic. Listen to a 6-year-old tell a story sometime—every sentence starts with, “Aaaaand …” Is that how you want your writing to read/sound?
Limit the times you use “and/but/or” to begin a sentence. It’s invariably best to nix the conjunction if you start your sentence with an independent clause: “In the case of Boffo soap flakes, the packaging …” You’re already guiding your reader to your next point, so putting “And” at the beginning just dilutes your writing.