Don't Stress over the Mess
This eating thing is supposed to be fun. If the messiness is making you crazy, turn up the heat, strip her down to her diaper, and put a towel or shower curtain (for wider coverage) under her chair.
Wash and save your glass baby food jars. You can use them to store homemade baby food, a meal-sized portion of food for travel, or a serving's worth of dry baby cereal — simply add liquid when you're ready. (Later on, they make great bug keepers for older kids.)
Moms who have the easiest time with the mess that comes with feeding a baby are the ones who own a dog, preferably a big one, with an omnivorous palate. Such dogs position themselves strategically under the highchair and lap up any spills as soon as they hit the ground. These moms say they wouldn't feed a baby without one. If you don't have a pooch, there are always newspapers, towels, a plastic mat, or just a mop to clean up the remains on the floor. If you're really lucky and the weather's cooperative, feed your baby outside. Hose down the highchair and area under it afterward. (Remember to remove your baby first.)