I'm still nursing my 19 month olds (although they are down to just 3 times a day or so most days). Talking to other mamas IRL helped (and seeing another mama nurse twins helped) as did reading this board and the APMultiples Yahoo groups, and I couldn't have done it without the EZ2nurse pillow, and a sense that nursing would pretty much be all I did those first months (along with making sure my then 3yo didn't feel too lost in the chaos).
Through no doing of my own, my girls had no trouble latching, and so I was able to tandem pretty much from the beginning (which makes it feeling like you are only nursing 90 percent of the time, instead of all the time!). I was not opposed to supplementing if needed -- in fact, I slowly introducing bottles -- both with pumped milk and formula -- at around 6 weeks, and kept trying once a week, but they never liked them, so I just kept nursing.
Get lots of help -- people to bring you food, clean your house, take your dog for a walk, whatever -- and spend those firstweeks figuring the nursing out. It is wonderful, and really helped me to connect to my babes (I still worry that each gets short-shrifted because of being a twin, but at least nursing gives them that contact, skin to skin, and slows you down long enough to marvel at the miracle of multiples.)