What a question! In many cases, when people are talking about non-monogamy relationships that are sexual, they envision awkward scenes that happen in movies and a lot of potential drama. This can happen, though with proper communication, many people find sexual non-monogamous relationships to be highly successful. There is something liberating about letting your partner know that you are okay with them having sex with other people. 

There is often an expectation, however, that both people will be on the same page the entire time. Keep in mind that your partner may have different viewpoints on non-monogamous relationships, and look to be nonjudgmental about them. It can take a lot of courage to bring up fantasies and fetishes with other people. Also, keep in mind that there are multiple types of non-monogamous relationships, even within the realm of sexual relationships. 

Not all non-monogamous relationships are sexual in nature, though there are some communities where these relationships tend to be a bit more physical. This can include things like swinging and swapping.

Overall, polyamorous relationships are very similar to monogamous relationships when it comes to success. People will have many individual relationships that do not work, and a number of them that do. Sometimes over time, relationships will end and a new person will be introduced into your life. Things can seem a little more fast-paced with sexual non-monogamous relationships, and because there are so many different ways they can be successfully done, communication is essential.

Dating multiple people can take a little bit more time management as well, another consideration overall. If you want to be in an open relationship, where sex with other people is accepted, communication is key. It is best to communicate with sex friends and partners before opening up the relationship and having sex with other people. Consent and communication are essential parts of relationships, and doing communications and consent right is a key part of maintaining these relationships you are in. For some people, non-monogamous sexual relationships are more successful than others. If you have curiosity, approach the concept tactfully with each person it concerns.