All good advise, but I'll add a few and try to clarify one.
You are significantly shifting the center of gravity rearward with a passenger, you are also raising it. As such, the bike is more tail heavy, and top heavy. When you pack for a trip, put as much of the heavy items in the saddle bags, and put the light stuff in the Tour Pac. Also, Put heavier items as far forward in both the bags and especially the Tour Pac as you can.
For lack of a better word, when loaded an two-up, the bike is more "sluggish". All inputs are going to be slower, and take longer. You don't accelerate nor stop as fast, and handling is affected. Make sure you plan for it.
As far as your wife leaning with you, I respectfully disagree. You are riding the bike, not your wife. Your wife should't move around any more than your luggage should. If your wife is anticipating a turn, and starts leaning before you are ready, it's going to throw you off your intended line (early entry). Now that said, many first time passengers get freaked out when you lean into a turn, and as the bike leans over, they try and sit back upright in the opposite direction. That, will Really throw the line off. Caution her to try and avoid doing that, and tell her not to try and help you turn by leaning into the corners. Just tell her to remain neutral, and let you do the leaning.
I strongly recommend an intercom as well. My wife and I have ridden with several different makes and models over the last 20 years, and well over 100K miles. Remember, she can't see much in front of her, just off to the sides and the back of your helmet. The intercom helps let her know what's coming; "Bump, three seconds" or "Stopping for gas at the Chevron on the right". It's also helps to have the second set of eyes, especially on a less than straight road. You may be looking through the turn, and miss something off to the side of the road; "Deer, 3:00!" It's also safer, and a whole bunch easier, than yelling at each other at 70 MPH...
Lastly, as IdahoHacker said, you are responsible for two people now, so ride at 6/10's not 9/10's. If I put myself in the hospital, I'm an idiot. If I put myself and my wife in the hospital, well, that'd be tough to live with.
We love riding together, and like I said we have been all over the States and Canada 2-up. Sometimes it's just us, and sometimes it's with a group. My wife has become the de facto go-to girl in our riding group for advise on gear, clothing, packing and generally riding behind me...