Prefold Diapers are a great place to start for beginners, since they are so inexpensive, hold up well in the wash, and if you just tri-fold them in a cover are very easy to use.
This is my experience with several different types:
These are the first we used. Everyone says they are not good enough to actually use as diapers, but they were absorbent enough for Efrim up to about 5 mos. They are 10 for $10 at WalMart, and stay soft after a lot of washing (we only had ten most of this time).
First I ordered the regulars (12 for $6.99). These are 2x4x2, so they are of course totally useless as a diaper. I made burp rags for my sister in law with them. Next I tried the extra absorbent ones because they are still only $7.99/dz. They worked well for Efrim until he started wetting more when my milk came in for Julian, but I would not recommend them for naps, overnight, or heavy wetters. Also they got really rough after about 2 months, but if you used fleece liners or something this wouldn't matter, and they are very trim. babybestbuy.com
Chinese Diaper Service Quality-
What a difference DSQ makes! Cottonbabies.com has the best price I can find on these ($24/dz for premium). We ordered even ordered regulars by mistake, which are 4x6x4 instead of 4x8x4, and they have worked great. These are my first choice for Julian. They are so soft and trim, and last him about 3 hrs in the day time, and 4 or 5 at night.
Many sites have their own version of these, and most moms swear by Clotheez, from Greenmountaindiapers.com. I do like Clotheez, but I prefer Imagine, from Nickisdiapers.com because they are a bit cheaper, about an inch shorter (so they fit in all of Efrim's covers without folding over), and I actually think they a just a little bit softer. Either are good. I got organic, and they are my first choice for Efrim. Clotheez are $30/dz for organic mediums, and Imagine are $24/dz.
Econobum (One Size)-
I got 3 dozen of these as seconds for a very good price. If you order them in the kit they are about $1 a piece. They are crazy absorbent. I'm just not very big on one size. In medium and large covers Efrim still has to wear them sideways to fit the cover, so it is really bulky between his legs. Julian has some I trimmed the third section off, and while they are the same dimensions folded as the Chinese DSQ they are so much thicker. Also after about 6 months they are no longer very soft.
Fleece or Terry-
I would love to try some Bamboo or Hemp Fleece or Terry prefolds, since they take fewer layers for the same absorbency and the jersey is just so soft, but at $6-8 each it may be a while before I get some. Eventually though I'm going to order a bamboo 4 pack from Mandi's Menagerie on Hyenacart.com and will get a few hemp 3 layers from AMP whenever I get to try one of their duo pockets.
I trim all of my prefolds to fit lengthwise in a cover. If you use a wrap cover there is just no reason to bother with pinning, and I am not a big fan of the mess with pull on covers.
Hope this helps! Stay tuned for more cloth diaper how-to posts coming up.