How do you achieve this? How do you know he or she won't run off with someone else if they have the chance? Maybe he'll dump you and run off with that cute girl he fucked the other day. That's what happened with my first open relationship and what made it worse was he had my permission to fuck her, at least the first time. So I tried to do what everyone does, to learn from their relationship mistakes. The first open relationship was a young one in all meanings of the word, at least for me, it was my first boyfriend of any type, I was young, naΓ―ve and had only known him for about a month before I agreed to try something new. So I suggest you don't try adding spice to the relationship until you know you have a very solid one with your partner to start with.
If you don't trust them completely, with your life, your emotions, your mental health, or even the temptation that adding another person to your sex life will bring, don't do it. I can only say time and unique, often stressful situations will show you who your truest friends are. I'm not saying to put yourself in these situations voluntarily is a good idea, but I know my best friends have stood the test of time and been by my side when I needed a hug and a shoulder to cry on. I can only say I'm very lucky my current partner has been there for me as a good friend for years before we ever thought of starting this kind of relationship and it's probably the only reason this works for us.
2. Communicate openly and honestly with your partner
It's a great idea to talk to your partner about your sex life, I'm sure many of us can take a few cues from Hikergirl (great how-to by the way). Talk about what turns you on, your fantasies, what movie stars you would be naughty with if you could. And for many people that's as far as it needs to go. I see nothing wrong with that, discussing new things can turn you on and be foreplay for your own sex life with your partner, leading to a night of great sex and it may stop right there. But for some if the conversation keeps coming back to the ideas of including a third or fourth person or more in your relationship, temporarily or permanently, at least explore the idea. How would you go about it? Possible complications, concerns? If one person believes they would get too jealous or it's not for them the other person should respect that and not push their ideas on the other one, trying to force them to act out fantasies they don't want to happen, some things are not meant to be acted out and only to be dreamed of.
3. Be open minded and have fun, safely
However a time and place may happen when you have a partner you trust and has the same desire as you to try something new. In this case a three or four or moresome can work if a few ground rules are laid out.