I believe the first and foremost is the strength from within the couple facing it. You must be able to talk freely about desires, fears and ideas. If you can't achieve this you will have nobody to lean on to get through the darkest days - there are friends that may hold your hand but if your own significant other can't stand by you then what is your relationship really based on. I am lucky enough to be going through this journey with an involved and support husband.
The second things is a few close friends, maybe 3 or 4. All friends don't need the details. You need just a few friends with whom you discuss everything. I do mean everything. How is xyz procedure going, Side effects, The mucus between your legs, when is the next period, did you get it, how are you feeling, want to hang out cause I know this day has sucked for you. They provide an ear to listen or a conversation not related to your situation. Sometimes you are just tired of talking about it. But these select friends, these select friends really care. You can pick these people any way you see fit just make sure you can trust them without any doubt. You don't need them to share your icky details. I think it also helps to let them know about each other so if they want to talk about you at least they are talking to someone that knows all the icky stuff too. Because let's be honest, humans like to gossip. If you don't want them to gossip then isolate them, make sure they don't know about each other then if you can truly trust them they won't speak a word to anyone.
Third: You need a second circle of friends. These are the ones that know selected details you have chosen to share. They don't know every icky detail or every time you have mildly freaked out. They just know a generalized version of what is going on. They are the ones that ask questions and you answer or tell them you don't want to talk about it - either choice you make so them is ok. They can also provide a different outlook because sometimes it's nice to talk to someone that doesn't know your period should be here in the next two days. It provides a different kind of mental break. It is nice to have friends that really care but are comfortable not knowing everything. It does help it you know at 1 or 2 of them could move into the category of knowing everything if you choose.
Fourth: General people. People that know but not because you have had a heart to heart. They know, you know that they know but they don't ask how it's going unless you bring it up. They provide normalcy in society. I find these people are the ones that say how brave you are, how much it sucks or nothing at all. Sometimes it feels like getting a hug from a stranger. It is oddly awesome!
Fifth: Honesty. This really could be listed as #2. Honesty with yourself is so important. It puts you in a clearly and happier state of mind. Lying to yourself gets you nowhere. For the longest time I pretended I didn't have a miscarriage, it was easier to lie to myself then deal with it but the trade off for your peace of mind isn't worth it. The more you can take your head out of the sand the better you are able to think and process ideas and feelings. Although we have been struggling for 25 months now my head was honestly in the sand up until a month ago. I was just going through the motions and doing whatever I need under a cloak of darkness, after all I didn't talk about it.