You can have one gal kiss you on the strikes, and another kiss you on the balls.
But seriously.... Be well rested and hydrated. Two gals can be a handful. It's good that the two gals know each other well. That chemistry is important.Relative newbie here. Booked my first ever double for tonight, hobby or civilian, for an hour (money is too tight to do longer). Any tips to make it the best possible experience? I've seen one of the providers before, but have never met her friend.
You can have one gal kiss you on the strikes, and another kiss you on the balls.
But seriously....
Be well rested and hydrated. Two gals can be a handful.
It's good that the two gals know each other well. That chemistry is important.
If you have never enjoyed a threesome before, the one thing that safety requires that can put a damper on the experience is the time wasted changing condoms each time you switch partners. Using female condoms will take care of that little problem and allow you to be as debaucherous as you care to be.
Aside from that, just have fun at let the session flow naturally. Since you say you have seen one of the ladies and she is bringing her "friend" I think it's safe to assume they have done this together before, just let them take the lead and enjoy would be my only other suggestion.
to enjoy two wonderful and talented ladies. Your 1 hr. experience will only wet your appetite for your next FMF.
Enjoy!
Unfortunately I'm still in my 20s so I don't make the kind of money most hobbyists seem to be able to throw around 
Personally, I disagree with KK and I can have quite a good time in an hour.
There are some matters as to etiquette, safety, TER rules etc where you are going to get some very good advice here, and on these matters you should most definitely listen to the advice given by our "elder statesmen" lol. Advice on how YOU should enjoy your time and your money are quite frankly none of our business and are purely a matter of personal taste. Additionally, some guys are going to undoubtedly tell you that you are "too young" to be doing this and that you should be getting free pussy at your age. My suggestion when that happens will depend on what board you happen to be on when it happens. If it happens on GD, by all means tell the well meaning, but idiotic naysayers to simply "Go Fuck Themselves". If it happens here, you need to be nice and thing of nicer ways to tell people to "Go Fuck Themselves" lol
Back to your upcoming threesome, have fun and don't put a lot of pressure on yourself. Just let things happen naturally and you will have a great time.
Now go have fun young whippersnapper. lol
Haha, well I'm in a pretty bad dry spell in my late 20s with a lot of things I've never experienced like doubles or greek or a girl who makes my pleasure the priority. The dating apps are a tough numbers game, and I got sick of the drama after a few civilians who were just about sure things bailed on me. I said fuck it and here I am getting the sure thing just wishing I could do it more often! I can understand all perspectives of it, which is why I'll never tell anyone I know that I've resorted to this taboo lifestyle. I don't feel any shame other than taking a hit on my savings instead of getting closer to buying a condo. I can't live it up like all of you gents yet, but this stuff is awesome so I want to partake in what I can. Thanks for the advice my man!