Be sure to make the clothing appropriate for the age of the child. For an infant install snaps in the legs to make diaper changes quick and easy. It doesn't matter how great an outfit looks, if you have to pull it over a crying baby's head six times a day, you will pick a different outfit next time. For young children, make the clothing simple so they can dress themselves without difficulty. Use elastic waist bands rather than fly zippers and buttons to reduce frustration during those mad dashes to the bathroom when potty-training.
Children grow so fast and they are hard on their clothes.
Since you are putting a lot of time and creative energy into making their clothes, you will want to ensure that they last. Add length on pants and sleeves by making roll-up cuffs in a contrasting color. Make dresses for girls longer with drop waists allowing them to last another season. If cuffs on a long sleeve shirt wear out, shorten the sleeves and make it in to a T-shirt. Lengthen straps on overalls and use overall clips to allow for adjustment.