Texts, tweets, instant messages, e-mails, and visual presentations featuring bulleted lists are relatively new on the scene, and the grammatical rules governing them are still evolving. Nevertheless, most people agree that you should avoid these mistakes:
Unclear abbreviations: Especially when you're "typing" on a keyboard the size of a fingernail, it's tempting to abbreviate. Go for it, as long as you're sure the person reading your message will understand what you're trying to say. Remember cao. (See how this works? Cao is a made-up abbreviation, used nowhere but here, for "common abbreviations only.")
Dropping elements essential to your meaning: Don't drop a word or punctuation mark that adds an important fact. Dinner 8 p.m. may be a command or an assumption. Dinner 8 p.m.? is an invitation.
Inappropriate level of formality: Powerful people can break as many grammar rules as they want, as long as the meaning is clear. If you're writing or presenting information to someone with more power, however, be careful. Bulleted lists should be parallel, capital letters should be in their proper place, and punctuation should be inserted as needed.