So much to say and so little time.
First and foremost you should be confident in your demeanor. If you appear insecure or unsure the games participants will most certainly pick up on it and try to eat you alive. Be short and to the point while holding the plate conference. There's no need to ramble on about unecessary items, so just cover the basics. Regardless of the experience level of your partner you need to take charge of the plate conference. You don't want to be cocky, but you don't want to be a puss either. If you handle yourself like you're in charge and you belong there then you'll get an instant measure of respect.
Remember, the flow of the game is yours to control. That means you need to be hustling on every play. The players see you hustling and they'll pretty much follow your lead. Don't do anything other than go immediately to the foul line on the half inning switch and start seeing to it they're getting out onto the field. It's then your job to count the warm up pitches and keep the game moving. Nothing looks worse than a PU who goes over to the fence on a half inning and starts shooting the breeze with a spectator.
You say you're confident in your ability to call balls and strikes. That's great. Just remember to slow down when your calling pitches. The biggest problems newer umpires have with calling a good zone is almost always related to their timing. Track the ball all the way to the mitt, see it hit the mitt, read the label on the mitt, then call it.
Communication is key in a two man system. This starts by holding a thorough pre game meeting with your partner. Make sure you go over all coverages and signals the two of you will be using. During the game you want to make eye contact with your partner as often as you can to be sure your both on the same page. In a two man you're the one who is in charge of initiating all situational signals such as first to third, IFF, timing plays, etc...
As you're new behind the dish I would say you shouldn't get overly concerned with calling every balk in the book. The obvious balks will call themselves. You really need to be focused on calling pitches. Calling balks the right way only comes with experience. Also don't get caught up worrying about all the third world BS we discuss here. 90% of what you'll be calling are going to be the big six. Ball/strike...fair/foul...out/safe.........
Good luck!
Tim.