Every parent knows their baby best, but as a general rule of thumb, newborns need 10-12 diaper changes/day (aprox. every 2 hours) and older babies and toddlers require 6-8 changes/day (aprox. every 3-4 hours). The easiest way to remember is to change baby every time they have a meal or a snack. This roughly coincides with the number of diaper changes they will need. *Note this goes for any baby regardless of whether they are in disposables or cloth diapers*. Just because a disposable might be able to hold more, doesn't mean it shouldn't be changed with reasonable frequency too. Think of what you would like if you were in diapers ;)
Heavy wetting babies need more absorbency or more frequent changes.
Change baby as soon as possible whenever they have a dirty diaper (ie. poo). Newborns tend to poo very frequently, 24 hours a day, so this means you will be changing them at night too. Once baby gets older and begins solids, they tend not to poo at night anymore and can remain in the same diaper for as long as they sleep. No need to wake a sleeping baby just to change them. A second insert or booster can be added to the diaper to extend the time between changes for naps or nighttime with older babies. We recommend fitted cloth diapers with covers for naps and nights to provide the extra absorbency needed for longer stretches between changes, especially once baby starts sleeping for longer through the night. More about successful nighttime cloth diapering here.
To find out how many cloth diapers you'll need to diaper your baby, go here.