I HATE rules but I think these ones are pretty darned dead on!!!!
1. Don't use abbrevs. Part of the reason why sexting is so hot is because when you read a sext, it's as if the sender is talking dirty to you. This is why, when sexting, it's important to use full words and speak verbatim. In the middle of a sac-sesh, you would never use abbreviations to talk to dirty, so don't use them in a sext to cut back letters. It takes away from the whole point of sexting. Oh, and it also makes you look lazy, and if someone wants to bed you, they would rather know you will go the extra mile. Rule of thumb: Type it just as you would say it.
2. Don't use big words. The whole point of sexting is to be flirtatious and tempt the fella of your fancy with words to make him crave you. Using big words or innuendos might throw him off, especially when the dude has no idea WTF you're talking about. Save innuendos, lines and big words for the texts you send your friends. When sexting, the more direct and clear your words and intentions are, the better.
3. Be playful. Nothing captures someone's attention like quick wit. Use a pun when possible when initiating sexting. This will throw him off, because what you say can have double meaning. For example, if he's describing a new item he just bought, you can ask, "How big is it? ;)" If he's into you, he'll interpret it the naughty way, therefore making him initiate the actual sexting if he's into it. This puts the ball in his court, just where you want it to be.
4. Be wary of auto-correct. The second you send a sext with a misspelled word (or a word that wasn't meant to be shared in the first place) is the same second you ruin the mood. It's a total buzz kill, and even if you make a joke out of it, that caught-up, steamy mode you were both in totally changes. Before pressing send, re-read your text and be wary of auto-correct and misspelled words.
5. Know your audience. Being on the recipient end of a sext is really rather ego-boosting, and when people get a steamy sext message, they are likely to want to "show off" by sharing it with friends. Before you send a sext, keep in mind that there's potential for it to be shared amongst your guy's friends. Don't say anything too incriminating, and don't send something that you wouldn't want someone else to hear (or associate you with). Keep it tame, if you're concerned.
6. Know when to stop. If you've had some back and forth banter via sexting and then, out of nowhere, the recipient stops responding, let it go. If you text "Why did you stop messaging?", "Where did you go?" or "Why did you leave me high and dry?", you not only come off looking desperate, but a bit aggressive too. When trying to keep someone interested, know that the power lies with the one who ends the conversation first. Just like you wouldn't overstay your welcome at a party or event, get out of the conversation when you no longer have much to say or it's starting to drag on.
7. Delete your history. When you keep various message windows open in your phone or have various texts stored, you run the risk of accidentally sending the sext to the wrong person. I remember once sexting a guy who donned the same name as my brother-in-law. I didn't realize I sent it to the wrong person until the morning after, when my brother-in-law texted me saying "Good night? ;)" I was mortified! By deleting other conversations, you don't run the risk of your sext getting into the wrong hands.