How birth-order affects relationships.

Birth order, basically where a girl's birth falls in comparison with any brothers or sisters, is a helpful indicator of her personality, and therefore, your long-term compatibility together. And most woman will offer up this information willingly if you ask (or you can get it by stealing her license).

The Birth Order Book: Why You Are The Way You Are.

The order in which you and your siblings were born has a profound impact on how you act. Family relationships are the ones you've been in the longest, and are the ones you're the most familiar with (if not the most comfortable dealing with). Obviously, it's helpful to know how position influenced your potential life-mate's personality, too.

The Birth Order Effect: How to Better Understand Yourself and Others.

People generally fall into the four different categories: First-borns, Middle-borns, Last-borns and Only-Children. (Middle-borns includes any sibling that isn't the oldest or youngest.) And each carries its own particular traits and attitudes.

For example, Only-children tend to be organized, dependable, comfortable with responsibility and people who get the job done. On the other hand, they can also be a pain-in-the-ass, spoiled, demanding bitches who never admit to being wrong.

First-borns tend to be the responsible, take-charge leader types; textbook Type-A personalities. Over-achievers with an air of superiority, they need to be in control because they don't trust anyone else to do anything as well as themselves. First-borns are picky, insensitive, bossy bitches who think they know it all.

Middle-born's are often peace-keepers who hate confrontation. They're very practical and eager to be liked. Less driven than First-borns, they can quickly become codependent attention-whores who try to please everyone since they aren't good at making unpopular decisions.

Last-borns usually have strong intuitive 'people skills' and make friends easily. They tend to be social and extroverted, but still fear rejection. They have a short-attention span, bore easily and can be irresponsible, self-centered bitches.

As you can see, birth-order shapes a woman's personality in ways that are important for you to know about. Compatibility in this area is key. Luckily, determining which position works best with which is pretty simple using basic, common sense: In general, you want to avoid women who were born in the same position as you were.

The New Birth Order Book: Why You Are the Way You Are.

Are you a First-born? Then you might want to avoid other First-borns—you can't have two leaders without some ugly power struggles.

Are you a Middle-born? Again, avoid other Middle-borns—one of you needs to know where the hell you're both going.

Are you a Last-born? Avoid other Last-borns—somebody has to make sure the rent gets paid.

So which combos work best? Well, some of the better combos involve Only children with Last-borns, First-borns with Last-borns and Middle-borns with Last-borns, but others are possible, too.

Knowing what types to avoid is the most useful information as it can help weed out problem dates before you get too serious.

Yet there are even more compatibility factors that you can figure out with a little extra effort.