This may sound too obvious for words, but it's still important: the key behind making polyamory work is to be in a relationship where each person involved believes in the idea from the start. Pressuring somebody in the slightest to be involved in such a relationship is almost guaranteed to create resentment and unease.
For the potential polyamorist, remember: the vast majority of people are offended by the very idea of being openly in love with multiple people. This will make your pool of potential mates limited, even (or especially) if you are able to find one special partner who agrees to an open relationship. Think of how limited the options are for many gays and lesbians, and then realize that your options are perhaps even smaller. On the other hand, finding someone else for whom the idea makes perfect sense can be such a liberating experience that it can make the ensuing relationship exceptional even if it remains monogamous by default. In many ways, being with one other person who believes wholeheartedly in polyamory can be significantly more fulfilling than being with many people who are uneasy with it.
And hey, if you do find more than one person who fits this criteria, go you.
As a side note, probably the single best part about being in a polyamorous relationship with someone is the trust factor. Let's face it: if the person you are with not only doesn't hide from you the fact that he or she is sleeping with and/or in love with somebody else, but openly and joyfully proclaims it, then you can trust that person to tell you pretty much anything.