Jealousy is a very difficult and personal topic. We want to start by saying that it’s a very natural emotion and even can be healthy when managed properly.
In a nutshell, the best ways to combat jealousy is with trust and communication; but there’s so much more to it than just that. Anytime a relationship is opened up, the core of that relationship will be magnified. If you have a solid core, it will become stronger. However, if there are cracks and faults, those will become crevices and canyons. It’s best to be sure you have the most solid core you can. The more trust there is between you and your partner, the easier it will be to stave off jealousy. Trusting that your partner will adhere to whatever rules and boundaries are set up, and trusting that they will always come home to you, alleviates the stress when one partner is out with someone else. This trust makes the open relationship a lot easier and more fun.
As mentioned, communication is the other biggest way to help keep jealousy in check. The two of us communicate about everything—perhaps more than most people are comfortable with. We search for other potential partners together. We discuss what we like and don’t like, and what we want to experience. When chat starts, we are very open about that and don’t hide anything, both in text and in the emotions surrounding. Same thing when date time comes along. If we are seeing someone separately, the other partner always knows where and when the date is, and an expected time to be home (or just late—past bedtime). Then afterward (maybe the next day) we debrief on the date, whether it was a couple date together or a separate date. Part of what brings on jealousy is not knowing what could happen, what happened, how they felt about it, where it may go in the future, etc. It’s the not knowing that is hard; your imagination can be your worst enemy. And there are times that we fuck up and don’t communicate well. That can cause stressful times and hurt feelings, which we then work through and try to learn from.
Also, don’t forget to make time for just you and your partner. Your relationship is special and needs to be nurtured. Open relationships can take a bit of work and time (time to find people, meet people, date, etc). Don’t allow the time spent there to cause your primary relationship to suffer. Your primary relationship should always take preference.
Another piece of advice is to adapt the way you look at situations. Have you heard the term compersion? It’s the opposite side of the coin to jealousy. For example, rather than being jealous when someone checks out your partner, be proud. Instead of thinking that they are trying to take your partner from you, think of it that your partner is so attractive/funny/quirky/etc that other people are also interested. And out of all those people, your partner chose to be with you. You are so special for that. A small shift in the perspective of a situation can make it much more positive and healthy.
Finally, when looking at friends in an open relationship, it is easy to see that they are so in love with each other, yet we might miss the amount of work that goes into the relationship. Open relationships aren’t easy, but understanding and mitigating jealousy is the first step in making an open relationship look effortless.