Some factors you may keep in mind when choosing a pillow case for your toddler include the price, colors, fabric, and thread count of options being considered. There is no right or wrong way to go about choosing a toddler pillow case. You should choose one that meets your needs and matches your own style, whatever that may be. It's also a good idea to let your toddler, if the child you're buying for is yours, help pick out his or her own pillow case.
If you already have a bedspread and other decor items picked out for your child's room, you may pick out a toddler pillow case to match. Even if you didn't buy the bedding as part of a set, you may be able to find a pillow case to match the other bedding items you purchased. If you haven't purchased bedding yet, you may consider purchasing an entire set at once with the pillow case already included.
Another factor to consider when deciding on a toddler pillow case is the size of the pillow. Some toddler bedding sets come with full sized items, while others are smaller. If your child is sleeping in a twin sized bed, you should probably get a pillow case that is made to fit a standard pillow. Smaller pillows may be used with toddler beds, but if you want to use the pillow case even after your child outgrows her bed, then a standard size is probably still your best bet.
The fabric of your toddler pillow case is also something to think about. You'll obviously want it to be soft and comfortable if your child will be sleeping directly on it. Cotton and microfiber are two fabrics that are known for superior softness. This aspect won't matter as much if you are buying pillow shams to use just for looks with a softer case underneath, since no one will be sleeping directly on the sham. In either case, you should also choose one that is durable, machine washable, and stain-resistant so that it can withstand a messy toddler.
Colors and style options are entirely up to you. It's often a good idea to enlist the help of your child when picking out a toddler pillow case, though, since it will make her feel as though her sleep space is truly hers. Young kids love choosing their own decor items, and a pillow case is small enough to not matter if it's a little off the wall in appearance.