Tone is everything.
I'm sure you can relate to receiving a text and not quite knowing how to interpret it. Did he mean that sarcastically? Was she making a joke? It can sometimes be so hard to discern which is why you must strive to make yourself crystal clear. Always err on the side of caution and be explicit.
There's no need to yell.
Sometimes I am a fan of all capitals when I'm texting with close friends who know my texting style and want to make a point. When texting anyone beside your best friends I would recommend that you refrain from tons of exclamation points and all caps.
No double texting (unless absolutely necessary).
If you don't get a response right away don't bombard someone with tons of messages. They might be in the middle of something and your disruption is sure to be unwelcome. If you're dealing with something timely, then go ahead and use your judgement to determine if it calls for another text.
Don't be afraid to call.
If I am trying to work out plans with a friend and we just keep going back and forth with texts but aren't really getting anywhere, I call. Believe it or not, you'll sort everything out faster which will make both you and your friend grateful.
If you're asked a question, respond.
Ceasing to respond during a conversation, especially when asked a question, is unacceptable. If you were talking in person you wouldn't just walk away, so this is no different. Be courteous and if you need to end a conversation just say so.
What do you think of these texting guidelines? Did I miss anything?