Congrats! How wonderful. My sister has twins and they are fab.
I'm fairly new to cloth, and have just one 4 month old, so I'm not as experienced as many on here. Obviously I don't know what your situation is re help and money, but assuming with twins both might be an issue, this would be my thinking.
+ research now! So you've got your head round some of the options before you have the twins. This forum is great, I also find the one on Mumsnet helpful, and also some of the online shops have excellent guides (i.e. fill your pants, twinkle twinkle, cheeks and cherries).
+ aim to use disposables for the first three months. You will be v. tired, you want as many people to be able to help you nappy change as possible without giving instructions, and your girls will be small so probably won't fit birth to potty nappies well. If you feel up for changing to cloth earlier than three months then great, but probably better that than starting all eager and then finding it too much. I also think it would be quite expensive to buy newborn sized nappies when you are dealing with two babies... of course you can sell on etc etc, but you will be busy.
+ Reusable wipes are great, and I would ask for them as a present from someone. The cheekywipes full set with one extra pack of wipes should do you, and since they go in with the normal washing it's really no extra work and they are fab.
+ Obviously there are a range of different nappies that might be good for you, so trial some second hand or get a trial pack. Must admit I find the bumgenious flips great, and cost effective because you only have to change the wraps when dirty rather than when just wet. Essentially if you think you need about 15-20 nappies per baby you just buy that number of inserts, and about a third that number of wraps (this will make sense when you see the nappies! They are a 2 in 1 type, and birth to potty). Also not too bulky on small babies and not too bulky to carry round with you when out and about. The main downside is that there don't seem to be many available second hand as they are quite newly released.
hope that helps! Have fun!