If you're going to be using natural fiber diapers, you will want to prep your diapers before you use them.
Prepping involves washing and drying the diapers several times before you use them to remove natural oils and help the fabric gain absorbency. You will want to use a small amount of detergent at least the first couple of times to help remove the oils. After that, you don't really have to use detergent. I didn't know that, so I used detergent each time. Either way works.
If you're using cotton prefolds, your diapers will come out of the package nice and flat and smooth, but when they are fully prepped, they will shrink some and quilt up and look like this...
The more you wash/dry them, the more pee they'll hold. I think I washed mine 6-7 times before I called it good.
I have a few hemp diapers too, and while they also need to be prepped, they will not quilt up like the ones in the picture. I found that I didn't wash them as many times to prep them (maybe just because I was so over prepping by the point that we introduced hemp into our stash). You'll notice that hemp takes a long time to dry. It gets better once they're fully prepped! Hemp just holds a lot more liquid than cotton, so the drying time will be different. Now that mine are fully prepped, they dry in the same amount of time as my cotton diapers. I don't know how that happened, but I'm not complaining.
If you want to use cloth and you haven't had your baby yet, I highly recommend doing the prepping before the baby comes. Trust me when I say that washing the same clean load of laundry over and over again 6 times is not going to be your idea of a good time when you're dealing with a newborn and all of the challenges that come along with adjusting to a new baby. You'll just be happy if you have any clean clothes to put on your own body and you won't want to waste your precious time and energy on prepping. At least that's how it went for me.
If your baby is already here, you can wash the diapers with some of your regular laundry when prepping them provided you are using cloth diaper safe laundry detergent and your clothes can be washed in hot water. Also, remember, NO FABRIC SOFTENER! In fact, if your clothes have fabric softener in them from a previous wash, I wouldn't wash diapers with them. That may be a little extreme, but we are completely fabric softener free now because I'm terrified of having to strip diapers. Like I needed a new phobia...