Monogamy can be a wonderful thing. Two people can achieve deep levels of intimacy by excluding physical and emotional relationships with other people, developing a partnership that can last a lifetime. But strict monogamy is not the only option, especially for those with the responsibility to be careful and educated about bringing other people into the relationship. Whether short or long term, bringing a third person into a romantic relationship, or being that third person, can be a rewarding experience. Of course, it's a narrow path through a minefield of potential emotional and physical problems. Here are some things you need to do before inviting someone else into your relationship, or joining someone else's established relationship.

Honesty, Honesty, Honesty

It's a fact that we have to make compromises in our relationships in order to make them work. Exclusivity is not one of those compromises. The only way, and I stress this, the only way a couple can successfully bring someone else into the relationship is if every person involved wants it to happen. A third is not a gift you give, a sacrifice you make or a bargaining chip for something you want. If any one of the three doesn't want it to happen, then just don't do it. Be open and completely above board on this topic. And if you're the potential third, stay away unless you're comfortable with the setup and your two new flames deliver the proposition with smiles on both of their faces.

Ground Rules

Spontaneity is grossly overrated. While the original couple has (hopefully) gotten comfortable with one another, the third is coming into this situation fresh and uninitiated. Before anything, physical or otherwise, takes place, set some boundaries. It's infinitely better to know what should and should not be done before it happens than it is to inadvertently break the rules. All parties involved are responsible for everyone else. There is no excuse for carelessness when people's hearts and bodies are set up like dominoes.

Safety First, Last and Everything In Between

Sex between three people is complicated enough that health and safety shouldn't be another source of worry. It is not okay to use the same condom on two different people, for example. If you're grown up enough to be having sex, you're grown up enough to visit a clean, reputable adult products store for an education and an array of polyamorous paraphernalia. Though I don't mean any inherent sexism in this remark, those sex shops that are owned and operated by women tend to be of the highest caliber. You'll know the good ones from the first second through the door.

A Conscientious Third is a Good Third

If you happen to be the +1 in this situation, you need to be comfortable with the fact that your needs, while important, do not take precedence over the core relationship. You need to be aware of when it's time for you to go home, when it's time for you to give the core couple their privacy, and ultimately when it's time for you to bow out completely. To paraphrase the nationally-renowned sex and relationship advice columnist Dan Savage, you might go to a poly wedding but you'll never go to a poly third anniversary party. Three-person relationships aren't built to last. Everyone needs to be comfortable with that from the beginning. Otherwise it's just hurtful self-delusion.

Have Fun

Sure, there's a lot of serious business involved with bringing on or being a third, but if you can't enjoy it, then what's the point? Whether it's for one night, one year, or something in between, remember that the purpose of this exercise is to have a positive experience. Poly for its own sake is simply irresponsible, but poly for the sake of a unique, fun experience can be very rewarding for everyone involved. Assuming everyone is on board, don't take the non-health, non-boundaries stuff too seriously.

It cannot be stressed enough that poly is an acquired taste. For those few couples who are genuinely interested in it, it can be a boon to the relationship. Still, this is varsity-level romantic behavior. If you're not interested in anything but one-on-one exclusivity you're not square or old-fashioned, you just don't have any interest in this admittedly complicated practice. As the saying goes, anything worth doing is worth doing right. The above suggestions are just a starting point. For those who are interested in this and other complex sex and romance issues, I recommend picking up a copy of The Ethical Slut: A Practical Guide To Polyamory, Open Relationships and Other Adventures by Dossie Easton and Janet W. Hardy. Rather than just positing theories, the book bases its claims on real-life experiences in a frank but accessible tone. It's hardly a how-to manual, but it's a good place to start before you dive in head-first.