Is already behind you:  Selecting the ladies.  If you want a good session, the ladies have to be comfortable with each other.  I'm not sure whether your idea of a duo is the ladies focusing just on you, or the ladies having fun with each other as well.  In the case of the former, it might be OK for the ladies to be nominally comfortable with the idea of being naked around each other, some light touching, a double-BBBJ and/or a little tease of each other here and there.  I imagine a lot of ladies are down with that.

In the case of the latter, you really need to have two ladies who are totally comfortable with having sex with another woman; I know that sounds obvious but a lot of providers talk a good game and then fail to deliver.  Always hard to judge, but I usually make it a point to see at least one of the ladies solo first to really gauge her comfort level.  Still, I've been lucky that in the last few years I've had duos where the ladies were 100% into girls and really indulged in each other.

As for the session itself, if the ladies haven't met before, maybe give them 10-15 minutes to get acquainted while you take a walk.  Perhaps bring a bottle of everyone's favorite libation to break the ice and chat for a bit to get warmed up.  Tell them up front what you want out of the session; either they will do it or they won't, but they can't read your mind.  Tell that joke you know to get everyone laughing and feeling relaxed.  And if you still feel a bit nervous, perhaps start with a 4-hand massage, a group shower, or some dirty dancing; whatever might help you to reduce the nervousness.  Mostly, take a deep breath and take charge; it's your hour to have fun.

... their favorite foods, liquor, and water (hopefully, no food allergies), but consume moderately if one would

 
Back in the days, I'd typically have them all dolled up, roles playing, and enjoying the treats afterward as we were famished.

 
Other than that, have a blast on your first duo!!

Be sure to write a review! I have had 3 duos and only one was good in the sense that the girls played with each other. So lookin g for a new one although I want to do an AMP but I dont think those girls are into each other and just do tag team.

Watch out for those knees and elbows!

I speak from experience, recent experience! Just last night, I had another threesome, and at one point when I was on my back with one woman on top of me, the other one beside us, the first one went to change positions just as I was starting to change my position too.  We became a tangled mess of six arms and six legs, but we all three laughed about it, slowed down, and made sure no one got elbowed in the eye, kneed in the groin, or knocked noggins.  Depending on how amorous and how vigorous the action might be, sometimes someone needscti direct traffic. One-on-one sex can sometimes have something similar to this, but add more people and you don't always know where everyone is going or what everyone is getting ready to do.  

This entire post is in lighthearted fun, just like last night's threesome. I hope you enjoy your first one.