There are a couple of very important things, that as an escort I’ve run across during my activity, that are extremely important to be discussed in advanced, so that all the parties involved can have a great experience together.
First of all, if you and your life partner are having a relationship based on honesty and trust, and the idea of having a threesome is on your mind, but you are kind of afraid to talk about it, just man up and be honest.
Nothing good comes out of repressed desires and feelings, so it is better to put things on the table, rather than hide them deep in your mind, always asking “what if”. And if your partner is up for it, then good for you! Start planning the event together, ask her advice when choosing the third person to join you, talk about how you envision things to happen, about limits, boundaries and so on.