We will assume that you have already read the information about the different parts of a cloth nappy and the different kinds... (if you have not, then read Understanding Cloth Nappies or this part will not make much sense).
In order to make the right choice, you need to consider your own needs and preferences. Here are some of the relevant factors:
Finding the right nappy requires some good advice from a nappy advisor or some research by you (probably the best place to start is on a cloth nappy discussion forum). But as an indication, this is how some of these factors play out.
A baby that does runny poos will be best off with a shaped nappy. If your baby is a heavy wetter, then you would be looking for the nappies with highest absorbency (shaped nappies over flat nappies, hemp over cotton, wool/fleece over PUL at least for overnight). The best fit will be with a snappi fastening, so if you have a baby with an odd shape (eg unusually long and skinny) you might consider this. Others can be adjusted separately at waist and legs, which is good if your baby's tummy and legs do not "match" - eg fat tummy and skinny legs, or vice versa.
If your baby has particularly sensitive skin, then you might choose natural fabrics (eg silk liners and wool covers) over synthetics.
Obviously, the less often you want to wash, the more nappies you will need. Most cloth nappy users would wash every 2-3 days. This would require around 12-20 nappies, depending on the age of the baby, and how fast you can get them washed and dried.
Fortunately in Australia, most of us are able to line-dry without too much trouble year round. On the occasional rainy day you can also use an indoor rack as backup though this takes a little extra space at those times. You might also invest in a few more terries as backup to allow for the longer drying time inside.
Flat nappies such as terries are by far the fastest to dry - you can hang them up at night and they are dry in the morning, and they may only take a quarter of an hour on the line on a hot day. Very thick shaped nappies with elastication will take longer - a full day in winter - and all-in-ones take the longest as the built-in cover prevents evaporation.
Most cloth users prefer shaped nappies over anything else, but they are more expensive. Whatever choice you make, do not think that disposables are an effective solution to the money problem. Some people will not pay the cost of a top-quality cover (around $20), but then cannot get through the night without leaks. So they use disposables instead, ignoring the fact that even just one disposable a night can add up to $20 in about 6 weeks or so (whereas the cover will last two years or more with daily use).
We believe that you just cannot afford to skimp on covers - it ends up costing you more money in disposable nappies to compensate, or extra washing to deal with the leaks. The real way to cut down on cost is to use flat nappies (either all the time or just some of the time), fleece liners and washable wipes. You can also look at the washing powder you use (both the type and the amount), the type of wash (how much hot water and extra rinsing) and of course drying (tumble drying being potentially the biggest single cost in using cloth nappies).
There is no doubt that, despite the huge savings in the long run, cloth nappies represent a big upfront cost compared with disposables. Some nappy sellers have a payment plan which you can use to distribute the cost over several months. Or you might start with terries, and gradually save up for some shaped nappies as time goes on. As we said before though, do not be fooled into using disposables as a solution to the cost problem - in the long run they will cost you much, much more.
Shaped nappies are the easiest to use - they fit around the baby with no folding, and can be fastened with hook and loop tape (such as Velcro and Aplix) or poppers that even the most incompetent nappy changer can deal with!
Poppers are a simple solution, easy to figure out, and pretty fast to use. Snappis are even faster. Some mothers-to-be are intimidated at the thought of using a snappi, but if this is you, believe us when we say - if you can use a zipper, you can use a snappi! It is honestly no more difficult than that, and given that snappis provide the best possible fit, it would be a pity to see people put off simply by unfamiliarity.
Velcro-type products are certainly the easiest and fastest way to fasten a nappy, and a lot of people prefer them for this reason. Elizabeth is a little put off by the fact that Velcro tends to look tatty faster than the nappy itself (something which is very noticeable after two years of daily washing!), and by the wide band of plastic that it puts onto the front of the nappy. However she also point out that there are occasions when under pressure that she is quite glad to pull out her only Velcro-fastening nappy and put it on in double quick time! Deborah on the other hand prefers hook and loop tapes, but usually only Aplix which is generally more suited to cloth nappying than Velcro. The two look identical to most people but are often of different qualities. With a slim and tall daughter Aplix fastenings allow for a snug fit at her small waist while poppers leave a very puffy look that doubles her width! Hook and loop tapes are also by far the best option for anyone with arthritis or a disability which affects their hands.
Flat nappies are the least user-friendly as they require folding before they are put on the baby, and some careful fastening if you want to get an extremely snug fit around the waist and legs. Snappis definitely take some of the work out of it and anyone who is willing to learn can put a terry nappy on extremely well. But there is no denying that it is a bit trickier, especially in an awkward situation (eg baby trying to crawl away).
Covers are also either hook and loop or popper fastening, and you will simply choose what suits you best. (Some covers are simply pulled on like a pair of pants - the downside being that pulling them off can get messy where a pasty poo is involved.)
Not much to explain here. Some people get a kick out of a washing line full of white terries fluttering in the breeze. Others prefer groovy tie-dye or zebra prints on their baby's bottom.
Some people also have an issue with the size of the nappy. We are both fans of big cuddly baby bottoms - the essence of babyhood! However, some people hate that look and therefore would go for a slimmer nappy (eg one made of flannelette or hemp) instead of, say, a Totsbots (one of the bulkier ones). Entirely up to you!
Most cloth nappies are made out of cotton, a fabric which does raise some environmental concerns, particularly about the use of pesticides and water. The terry towelling is often bleached, too. If you are particularly concerned about this, there are unbleached and organic cotton options, and even hemp nappies, available over the internet. You can also make a good environmental choice by knitting your own wool covers or dissecting and stitching an old 100% wool jumper. You might also choose your washing detergent and washing machine carefully, and take the environment into account in your choice of liners, covers and wipes.