http://www.angelfire.com/extreme/jkmeat/2timin.html
extrating some part from the link:
There comes a time in every man's life where he faces a choice: Choose between two chicks, or choose both. Choosing both can be a very tough row to hoe. Two-timing is an art form, and an art form of men. So, from us to you, a little guide to living large.
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Two-Timing Classifications
The Seasonal Two-Time
Seasonal two-timing is one of the easiest ways to get into the two-timing groove. Seasonal two-timing simply means that you only have one real girlfriend, but the girlfriend depends on the season. For example, let's say you are a college student whose home is in oh, let's say Iowa, and you're going to college in oh, let's say Tulsa, Oklahoma. So, growing up in Iowa, you have a girlfriend, whom you love, and you want to stay with in Tulsa. However, Tulsa is so far away that you get lonely without her. So, in Tulsa, you get yourself another girlfriend for the schoolyear. No harm, no foul. In fact, this wouldn't even have to be called two-timing if it wasn't for those punk girls and all of their rules. This is the perfect way to go also, because there's virtually no way you can get caught, unless you're an idiot.
The Casual Two-Time
This may also seem like a risk-free way to go, but the consequences can be brutal. This method means that you two-time, or even three-time but never officially commit to one of the girls. To a guy, this seems like a great way to go. No agreement on exclusivity, no reason for the girl to get mad. Right? Wrong! If you don't verbally commit, the girl will imagine that you meant to. She'll be just as pissed, only also very sad if she finds out. And that sadness will equal her and all of her friends coming at you. Bad news
The Back-Up Plan Two-Time
Occasionally us dopes will actually get the opportunity to go out with someone way out of our league. This can be dangerous,and the chances of it lasting probably aren't very good. But does that mean you say "No"? NO! At least not according to the Back-Up Plan Two-Timers (BUPTT's). Using the BUPTT Method means to get yourself another girlfriend, in your league. That way, when you're intimidated or scared of your goddess girlfriend, you can fall back on you loser girlfriend. And when the end inevitably comes, you're not single! But you are availbale
The Maniac Two-Time (aka: The Man's Hero Two-Time)
And we don't mean that in a bad way. The Maniac is the guy who just loves girls so much that one, or two, or three isn't/arent't enough. The Maniac just likes the ladies, as many as he can handle. The Maniac is also called "The Maniac" becaue there is so much stress associated with one chick that it is quite a task, or shall we say, "Endurance Test" to have more than 2.