a) Hire a house cleaner to do the bathrooms and the floors and a deep clean on the kitchen every 2 weeks. Get them started by the time your wife reaches the 7th month, because by then, you'll already think you are overworked and you'll think that your wife is just saying she can't get down on her hands and knees to clean the bathroom floor, even if she's already down there routinely, puking her guts out. Not that this ever happened in our house, but you'll find that you won't even want to make a joke like that by the seventh month. Either way, you'll have enough on your mind once the babies come that cleaning the bathrooms and the floor will be the last thing you'll have energy to do on your Saturday mornings.
b) Line up help for as long as you possibly can for after the babies arrive, and make sure every one knows what they are getting into. They are there to help, to do dishes, laundry, middle of the night baby holding, grocery store trips, phone call interceptor, anything that will give you and / or your wife even 10 more minutes of sleep. Make sure the people who are there to help are people you and your wife are comfortable being around 24 hours a day for days at a time. Your wife needs to be able to be fully exposed during feeding times, and she needs to be completely free to be able to do it, anywhere in the house. Have just one person there at a time if you can, and make sure that you limit visits for others to an hour here or there, and reserve the right to change the date and time at your whim and desire. Avoid having any other children that aren't your own in the house until the babies are 3 months old, especially if your babies are preemies, as many twins are. The first few months are all about the babies, the mom, and you (in that order), keeping everyone healthy, happy and sleeping as much as possible. It is your job as daddy to keep the external stresses and pressures during the last few months of pregnancy and the first few months after the birth to a bare minimum. We found that you need to have n+1 people in the house for baby care, when n is the number of babies due to arrive.
c) Make sure you always have at least a half full tank of gas, every day. I went to lunch one day, and had about an eighth of a tank left, and thought I'd be able to fill up on the way home. 45 minutes later, I was on the way to the hospital to meet my wife, and I had to pull off the interstate to fill up with gas so I didn't run out. Luckily I knew the area pretty well from my days hanging out at country bars, so I knew shortcuts to the hospital once I got off the highway.
d) Read the book "What to Expect when you're Expecting", but skip the really scary stuff in there. If the scary stuff does happen, nothing you read is going to prepare you for it. If the scary stuff doesn't happen, be happy you didn't worry about it.
e) Talk to your babies before they are born. It's an amazing thing to do, and it does help. Greet them with the same phrase every time you do it. Mine was "Hi
f) Go to all the ultrasounds you can. It's just amazing to see the development, and just makes the whole pregnancy thing more real for you.
g) Go out to dinner / movies / hang out with friends as much as you can possibly stand. Our twins are now six months old, and the only 'restaurant' my wife and I have gone to together since the birth is Starbucks. We now have long conversations about going out to our favorite Italian place, or reminisce about the crab wontons and plum sauce we had on our honeymoon in Hawaii, or the Bao we had in Chicago. It sorta-kinda gets us through the baby dinners of rice cereal with peas and pears mixed in. But not really.
h) Get a DVR to 'time-shift' your favorite TV shows. If the babies go down at 9:04 PM, your ass should be in bed by 9:12 PM, no later. It is totally not worth it to stay up even 20 minutes longer to watch the end of 'Lost' when you could be sleeping
i) Find someone who is 3-12 months ahead of you in the pregnancy/baby thing, and see if you can be the target of their hand me downs. It will save you a small fortune, and you'll get past the whole 'it's not new' thing really quickly when you see just how fast they grow out of stuff.
j) Get a digital video camera and a good still digital camera.
k) Start up a blog to share news with friends and family, and get used to posting. It makes it a lot easier to communicate with everyone, far and near.
l) Buy a freezer and stock it with meals, like casseroles, pasta like ravioli and home-made pasta sauce, ice cream bars, and whatever else you can fit in it. We really didn't start to dig into it until after our help started to leave, but it's a real saviour when you've already had your fill of pizza, teriyaki and sanwiches. Our favorites included: Souper Skillet Pasta (a family recipe I'll try to post here someday), Easy Chicken Chili, Red Beans and Rice, the aforementioned pasta sauce and store bought ravioli, tuna noodle casserole, and various soups.
m) Stock up your time off from work to take a t least 3 weeks after the kids are born. Now, if you live in a country/state where they insist you take time off for kids, or work for a reasonable company that says 'Having twins is not considered a vacation', then more power to you, but I had to fight and scream bloody murder to get my time off qualified under our Employee Illness Leave policy because I didn't give enough notice. Well forgive the fuck out of me for them being born 5 freaking weeks early. We didn't get enough freaking notice either. And yes, this is a bitter point of contention for me to this day, and the main reason I can't stand the business world in general these days.