K.,
First of all I want to say congratulations! Having twins can be such a wonderful blessing!!! When people ask me for advice in preparing for twins my first huge suggestion is to be sure to keep a record of your pregnancy and their first few months! Keeping a journal or blog and making sure you get some pictures of yourself well in advance are huge! The first few months tend to be a bit of a blur for most moms so be sure to jot down some thoughts and development about the twins every few days. You'll be tired, but it will be worth it.
The second most important thing I suggest is to try out different things to see what works for you and your family! There are many books out there that have very specific recommendations for the "right" way to do things and many parents of twins are also very opinionated about what worked for them, but that doesn't mean any of it will be right for you. Sure, read up, join your local Moms of Multiples group, there are many benefits and suggestions that can definitely make life easier.
What you will need will also greatly depend on your family situation. It did not work for us to have 2 swings for example. So having one swing, one bouncy seat and one exersaucer that we could rotate them through was great! I do recommend having 2 high chairs, 2 cribs, and 2 bumbos (of you want that sort of thing). For us, having the babies in the same crib until they were about 6 months old was fine. They definitely needed separate cribs (simply because of size) at that point, but it's different for everyone.
Clothes and blankets: Despite what some of the books recommend (they say you only need 1 1/2 of the usual wardrobe/baby care items to clothe/care for twins) ~ you definitely need double the number of onesies, jammies, socks, shoes (I sometimes even recommend that you have 3 pairs), slippers, towels, washcloths, diapers, wipes, bottles, sippy cups and other feeding items. As far as wardrobe is concerned, you may be able to get away with 1 1/2 the usual wardrobe here. Some families like to have their twins match or coordinate, in that case you need double the wardrobe as well.
Getting recommendations from other twin families is such a great way to get ideas that will lead you to the way that works for your family. Take it easy the last three months of your pregnancy. Try to get rid of as much stress as you can and don't do any heavy housework or child lifting ~ it's all about keeping those babies in as long as possible.
I wish you a great future with your little blessings!