The consistent pieces of the open puzzle seem to be honesty, communication, compersion, love, understanding, knowledge, and a good, agreed upon set of guidelines.
Communication seems obvious but this is more than just talking to each other. It has to be a brutally open line of communication about what you want, where the lines are drawn, and how opening the relationship makes you feel. It is a difficult decision to allow other people into your previously sanctified union. Doing so without this complete honesty, no matter how hard the conversations are, can lead to disastrous results.
Compersion is a word I have come to love. It is also a concept I have embraced for most of my life (without know the actual word for it). When I was 14 and in love with my best friend who was head over heels in love with Glenda the Good Witch. I hated that girl. It took me a couple of years and jealousy to the point that I almost took my own life to realize that hate and jealousy are wasted emotions. After that I couldn't keep hating her. She made him so happy. If I loved him like I said I did, how could I not be happy for him. So at that moment, when I was 16 I had my first run in with compersion. There have been many opportunities since then for me to practice compersion over jealousy.
Understanding and embracing compersion is a vital part of success. Do you stand a chance of losing them by allowing them this freedom to explore. Yes, you do.
Loving your primary partner and understanding that you are the main focus of each other's lives goes a long way to overcoming the difficulties with opening up to any degree. You must know that it is not a deficiency in either of you or your ability to satisfy each other that has you wanting to open up (and if it is, please stop here and go back to the drawing board), but just a bit of wanderlust and a need for variety. Since there is no way for us to be every single thing our partners will ever need, this is a good way to meet the needs of your partner and to take joy from those needs being met.
Knowledge comes from doing your homework, read the articles, the books, the blogs, the forums. Talk to people you know in the same type of openness.
Every open relationship is molded by the partners involved. You have to sit down and discuss who can you see, when can you see them, how will you find them, how much will you share with each other about your adventures, what is off limits, what safety precautions will you take, will there be veto power, can love be involved, is it purely sexual, are texting, email, phone calls ok and to what extent and when. There are so many bases to be covered. Find a good resource (and there are a few of them out there) and decide before the adventures begin what is ok and what is not.
So you have made the decision to open up and all the pieces have been brought to the table and discussed. Now what? Now to determine just what kind of openness you are comfortable with. This is where all my new friends have come in so handy.
Will you be the ones who help each other write dating site ads? Will you help each other find dates, discuss the possible new partners, leaving detailed information on the playmate with your SO (significant other), having overnight dates, and scheduling your calendar so that playdates don't overlap. Will you lustily and aggressively pursue external relationships where sex only or friends with benefits seem to be the primary goal, and as much as you can get as often as you can get it.
Maybe you'll know that external relationships have been approved to be explored but choose not to have an in-depth detailed knowledge of exactly how that is playing out with your partner as long as the agreed upon guidelines are being honored and you are getting what you need from the primary relationship? Dating site ads might be used here as a means to attempt to connect or it may be that relationships are explored if a connection is made online or in real life. Generally in this situation only what information is asked for is shared.
There is always the fuck buddy. Someone who is just there to provide a moment of variety, a sparkle of newness and excitement in your life. To be something different from the deep and intense relationship you have with your primary partner.
There are those who are officially classified as swingers but who are willing to use separate rooms. Going into a situation of swapping in separate rooms provides a way for each partner to fully engage themselves with their new partners without worrying about how their spouse will feel about seeing them with another. Plus it's kinda hot to think of the things your spouse may be doing in the other room and how lucky that person is to be receiving their attentions.
Maybe you will have only an occasional opening. This would be when one partner grants the other very specific permission to play with another person. The partners here are not free to pursue unfettered external relationships but after honest communication, permission may be granted for a certain person, time or place for solo playtime. Still here a set of guidelines needs to be in place to create a safe and fun play time that all parties can be satisfied with.
Whatever definition you chose to dress your new marital landscape with, be sure that you are honest with each other, keep the lines of communication open, play safe and always, always respect your primary relationship. Know what a blessing you have in a spouse who is willing to explore all avenues of life with you, one who would want you to have all you want out of life and who will gladly and honestly explore their own desires and wanderlust with your encouragement and acceptance supporting them.