A google of Texting Etiquette yields 885,000 hits. These are just a few.

• Use text messaging appropriately
• Text-messaging is not an alternative to using the phone when calling would be considered rude. You would not take a call in the middle of a movie, a performance, or a meeting, and likewise, you should not send text messages.
• You shouldn't use text messaging when informing someone of sad news, business matters, or urgent meetings, unless it's to set up a phone call on the subject.
• Don't text-message anything confidential, private, or potentially embarrassing. You never know when someone might be looking over your significant other's shoulder-or worse yet, when your message might get sent to the wrong person.
• Guidelines
• Do not call in response to a text message (BroCouncil Golden Rule).
  [I don't agree. I think there are occasions where you need to negotiate a response e.g. "Do you want to see a movie or go to dinner tonight?" where you need a longer conversation to answer, that a phone call is appropriate.]
• When you have a chance, respond to a text message with either a text message or a phone call. (per Emily Post)
• Make sure you're texting to the right phone number! It's very easy to dial the wrong number or select the wrong phone book entry.
• If you text-message someone who doesn't have your phone number, start your message by stating who you are: "Hi-it's Kate (yoga). ..."
• Just as you should not be answering your phone during a conversation, you should not send a text message when you are engaged with someone else. If you are with someone who will not stop text messaging during your conversation, feel free to excuse yourself until they have concluded their messaging.
• If you receive a text message that was sent to you by mistake, reply explaining that you aren't the intended recipient. You don't have to respond to anything else in the message.
• Finally, remember that as with email, you can't know for sure when the recipient is going to read his or her message-so don't freak out if your text message doesn't get an immediate response.
• Don't send group texts. Many people don't realize that they are replying to everyone when they respond to group texts,
• If you text someone two times and they don't respond, they don't want to talk to you. So stop texting them. Immediately. (Mother Nature Network)
• Always proofread.
• Abbreviations from BroCouncil-
  - If a woman sends you a 3 page text don's respond with "K". At least give her a full "ok."
  - Don't use "LOL" more than you have to; Sometimes a simple "haha" will do
  - Don't use "u" or "ur" unless you don't mind being thought of as an idiot.