YourTango.com put together a list of things to do before you sext a picture to a lover (Attention Brett Favre & Anthony Weiner!)
1) Be sexy. For guys, tumescence is of the essence. The so-called Brett Favre picture featured a flaccid wang book-ended by Crocs. I'm not sure of a more clear way to tell a woman that you're completely uninterested in her sexually than the combination of tacky sandal thingies and a soft thingy. For the ladies, maintain your best level of grooming, don't get too close and show some body.
2) Measure twice, cut once. Be absolutely sure that you're sending your whatever to the right person. Your mom might have a great sense of humor about these things, but there will be many questions in the vein of "what kind of person are you?"
3) Don't send dick pics (or snatch snaps) to people who absolutely don't want them. I'm not an "expert" on "the law," but it sounds as illegal as it is a bad idea to marry a guy named Peterson**.
4) Don't show your face. Plausible deniability goes a very long way. Ask Brett Favre. Just because a sexy photograph came from your account or phone, it doesn't rule out that it came from Google Images, was a goof or was produced with some sort of genitalia-uglying PhotoShop program.
5) Say "no" to quid pro quo. Sometimes life isn't fair, just because someone sends you a photo of their "stuff" doesn't mean you have to reciprocate OR use your real photo (see previous point). Extra hilarity points if you return the pic of a different ethnicity, gender or species than of yourself.