We have managed to cloth diaper them since they were about a month old. We initially started with disposables, just to make life a little less stressful in the beginning. Looking back, I really think we could have switched to cloth sooner, because it really doesn't add that much complexity to our lives.
We wanted to make cloth diapering as inexpensive as possible, so we just use the basics here - no fancy all-in-one diapers (though I admit it is so tempting to try them). In the beginning, I bought a set of newborn prefolds. Prefolds are basically just old school rectangular diapers that are made from cotton. (You can get them made from other more interesting materials, but we stick with 100% cotton.) To learn more about prefolds, check out this website.
The prefolds themselves are not waterproof, of course. They's just plain cotton, so they soak up the pee and hold it there, so you need a waterproof cover of some type to go over the prefold and keep your baby's clothes (and your clothes and everything else) from getting wet. There are a million different types of diaper covers that you can buy to cover prefolds. I bought a set of covers from a local work-at-home mom, Malia. Her company is called Bumbledoo, and she makes some really cute products and truly cares about her clients. I highly recommend checking out her store.
I also bought some Bummis Whisper Wraps from Craiglist and eBay. Craigslist and eBay are a great way to save money on all kinds of baby stuff, but especially on cloth diapers. We also have a handful of Proraps, and I like those a lot for our little girl. And, of course, we use our Bumbledoo covers as well. I use all of these on a daily basis and I like them all. They all have either adjustable velcro or snaps that allow us to tailor the size for our babies as they grow.
Now, we've bought larger prefolds as the babies have grown. We have to experiment with the different sizes to figure out which ones fit which baby best at their different stages of growth. I've ordered from CottonBabies.com and from Green Mountain Diapers. I've really liked both online stores.
There are so many different kinds of diapers out there - prefolds with covers, all-in-twos, all-in-ones, contours, and more. I remember being a little frustrated at first, because I didn't understand all the differences and I just wanted someone to tell me what the optimal diaper is (the engineer in me assumes that there must always be an optimal solution to every problem). The truth is, each type of diapers has a different level of cost and convenience. Prefolds, for example, are arguably the least convenient but also the least expensive way to diaper. All-in-ones are generally considered the most convenient but also the most expensive way to diaper. I recommend that you buy a few different kinds of diapers and try them out so that you can be sure of which type of diaper is the best fit for you. (Craigslist is a great way to sample different kinds of diapers and wraps.) We ultimately decided that cost was more important than convenience, and I don't consider prefolds to be all that inconvenient, personally.
I hope someone finds this post helpful. I've gotten a lot of questions about how we cloth diaper twins. It's really not difficult at all. I enjoy washing my little babies' diapers and feeling like I'm helping to preserve this gorgeous planet that God has given us.
I'm going to write another post later about how we wash our diapers. Right now, I think I have two babies upstairs who have woken up from their nap and are ready to play with Mommy!