Step 1: Obish
Playing this "game" well will make your speech near-unintelligible to people who don't know the trick to understanding this method of speech. To people who understand, your speech will come in loud and clear!
Please, remember that this mode of speech isn't unknown, it's just not widely known. So conferring "privately" with someone in front of a car salesman (who will likely know all the secret languages) or involving truly serious matters is not recommended. There are some people know this language, so it's really just PGP (pretty good privacy), and a bit of fun for you and your friends or significant others.
Step 2: How to Speak Obish
When pronouncing words, simply add "ob" before every vowel sound.
>Stobore (ob before vowel SOUNDS; the E at the end is not pronounced)
The pronounciations included dashes for help pronouncing, they do not imply a pause. Quite conversely, you must try to pronounce the sounds as close together as you can. If you take your time and sound the sylables out, people may figure out the trick.
>This guy's boring, help me out of this!
>Thob-iss gob-eye's bob-o-robing, hob-elp mob-ee obout (like "about" with an "o") ob-of thobis!
I can't imagine there's much else to say, except that once you get used to speaking like this, you'll be able to speak it without even thinking.
Step 3: Tricks and Tips
Speed is the trick to this language. Do not use it seriously until you and the person(s) you're speaking it with are fast enough.
Once you're sure-tongued with the language, try to adjust the pitch and pronounciation of the word to make it sound even less like the original word.
Short and common words that start with vowels are your enemies. These words will help people decypher your language. Words like "of" or "as" should be pronounced so fast that they are almost implied to the listener, but to make them even harder for people to understand, use other words that don't follow the ob rules. Replace "of" with "olive" or make "as" into "asbee". Try to choose something that is fast so as not to slow down the conversation. Names are a real danger, since people certainly know their own names, and if you start talking about Rob-ojer, Roger is going to figure out that you just added "ob" to his name. Use replacement words for names to keep people from catching on to the trick. Roger becomes Raybo, John becomes Joe-boe. Try to keep ob out of the special name to make sure the person you're talking to doesn't try to interpret the special name, but try to keep a "b" in there to keep the name sounding like the rest of the conversation. Of course, these special names must be agreed upon with your co-linguist beforehand.
These are really only necessary when using Obish in front of the same people over and over. If you're only going to be using it every once in a while, you don't need to add any of these tricks to the language to keep from being understood by those who don't know it. Keep in mind that the speed is always good, since if you're not fast with the language, you won't speak it, and then what good is it? :)