Get your minds out of the gutter- not that kind of practice haha!
Over the years, Husband and I have gotten to "practice" our parenting skills on our three nieces. We've had weekend visits, helped with feedings, planned lots of activities, changed diapers, and had the opportunity to watch my brothers and sisters-in-law parent. We've learned a lot from them, and various other parents we're friends with, and we both find ourselves observing "how it's done" more and more carefully.
I've learned there is no practice makes perfect, because each child is so different that you're constantly learning and adapting. I've learned that a sweet smile from a newborn usually means something not so sweet is coming out the other end. I've learned that boxes are better presents than the elaborate toys they hold. I've learned that no matter how many times you get up in a night, or tired you are, nothing compares to feeling the weight of a sleeping child in your arms.
I may not be as sentimental when it's night after night, but I hope I'll have the chance to come back to this post and laugh about how much I was looking forward to a lack of sleep.