Since the creation of genitals, the greatest thing to happen to adulterers is the invention of the smartphone. It's your own personal communication hub that you carry on your person, dissociated from any one time, place and potential interference from middle-men. No more passing phone calls through curious secretaries, no more mysterious hang-ups at home.
All of that, assuming you have a mobile phone made in the current century, comes packaged up with apps for services like Dropbox that you can use to send naughty pictures, or your filthy thoughts in your own recorded voice.
Having said all of that, there's absolutely nothing about your new electronic wingman that keeps you from being a complete fucking idiot with it. A tool is only as good as the person wielding it, and you can torch yourself just as easily with a careless call to a cell as you can by showing up at your playmate's workplace in bondage gear with a whip shoved up your ass.
Just like everything else about the successful affair, there are rules and practical guidelines to follow to avoid the day when you get your phone thrown at your face by an angry spouse. I'm going to include general communication practices as well.
Rule 1: Set a unique password or passcode.
If you just read the sentence above and slapped your forehead, turn in your phone and hang your head in shame. And don't set just any password or passcode - make it something that you don't use anywhere else. This is the key to the kingdom we're talking about - if someone can get into your phone or computer, they can see everything, so don't let it happen. You should also set your phone to auto-lock when you sleep it or after 1 minute, and you should always lock it before you set it down. Just make it a habit. Text girlfriend, lock phone, set down. Repeat.
Rule 2: Use uninteresting codewords.
Your contact card for your playmate shouldn't be their real name (unless they're also a friend or acquaintance you can explain - more about that in another post), and it also shouldn't be something flamingly obvious like MY FUCKBUNNY, as funny as I find that. Either pick a pseudonym you'll remember, or a simple phrase with meaning to you and your fuckbunny, but no one else. This way, when a text or other message appears on your phone's lock screen from "Dubuque Municipal" when your spouse picks it up, there's no sudden panic.
Rule 3: Minimize channels.
Don't conduct your dirty business on several devices. If at all possible, keep it restricted to one, and make that one your smartphone. Invest in a nice one, treat it well, and learn how to use it effectively.
The same goes for apps on that device - establish one or two means of regular contact (text, email, Skype, whatever) and stick to it. Try whenever possible to make that channel for your slutty partner only. Don't have a Skype account where your wife's contact is right next to everyone else's. If there's no one else to accidentally tap and send a message about the current state of your cock to, there's no chance of a message going astray and causing questions.
Rule 4: Take it, send it, delete it.
When you take a picture, and who doesn't want to send the occassional upskirt of themselves to an appreciative eye, take the picture, send it along to your playmate, then delete it off your phone. If you're intent on making a library of such things, use a service like Dropbox and observe the same protocol: take the picture of your cock, upload it, and delete it. Make sure that folder or app is double-protected by another password as well.
Rule 5: Don't play in mixed company.
This one is more difficult, because inspiration may strike at a moment's notice and suddenly you're telling your slutty friend about how much you want to throw them against a wall and maul them, and then your spouse or kids walk into the room. Don't finish the message, don't start dancing around like a loon trying to make sure no one can see the screen, because you look like an idiot - and idiot with something to hide.
Turn off the phone, set it down, and pay attention. Your filth will still be there when you get another opportunity to finish your thought.
Being smart doesn't come naturally to a lot of people, and that's why those people get caught. But you don't have to be smart to be safe - you need to make rules, follow those rules, and not break those rules without an actual reason, backed by an actual thought process. People don't get caught in their adultery because of the filthy things they do with other people (unless you're being extra stupid about sexual health and safety, a whole other topic). Adulterers get caught because of a breach in the flow of information, usually made because they started taking the privacy of that information for granted, and over-estimated their own cleverness.
Say it with me:
Don't get cocky.