I was told to aim for 24" X 36". So mine fall within that size--give or take 2" in each direction. I have had to adjust some patterns to get the desired size with the border (like Bonnie Hunter's "weed whacker"--mine is very different from what you see on her website--but it started with her pattern). I typically only use a 2" border. The only reason I even use a border is because it makes it easier to birth them without all those seams on the edges. Other than the size preferences, the only stipulation I've been give is for a "calm" backing fabric. And this is VERY IMPORTANT. That's why I chose a neutral flannel for the backing. The front can be anything you want so long as the back is calming. That way they can flip the quilt so the baby sees the front side when they want to stimulate the baby and flip it back to the calm side when the baby needs rest.