Check the developmental milestones for the ages that you're working with. There are different milestones for children at 8 months and 14 months, for example. A good place to start is with the American Academy of Pediatrics' "Developmental Stages" guide, listed under Resources.
Write down goals based on developmental milestones. For example, your goals may be to help a child learn to walk, enjoy reading or improve fine motor skills. These goals will vary based on the age.
Create general categories of activities for infants. You'll want to include gross and fine motor skills, musical appreciation, literacy, language development and social development. Again, these categories should be based on age. A 9-month-old baby may not be ready to focus on fine motor skills, for example.
Think of activities that fit in with each category. For large motor skills, you can include playing with push toys, throwing and kicking a ball, walking, running and ride on toys. Musical appreciation includes playing with simple instruments, listening to music and doing simple dances along with songs. Literacy might involve listening to stories, "reading" books on her own, singing the ABC song and learning basic phonics.
Plan activities throughout the day, but allow the child some choices. With your list of goals, categories and activities, you can loosely plan the day. For example, you may want to spend one day doing activities in the fine motor skills, musical appreciation and language development areas. You can then give the child choices within those categories. She can choose between playing ball or playing chase, singing a song or playing an instrument, or reading a book or telling a story.