Consider the purpose of your song. Will it be just for fun or will it be mainly for educational purposes?
Create a melody by humming or playing an instrument. Aim for a simple tune that is within a child's vocal range (from about middle C to the G above it) and can be memorized easily. You also could use a well-known melody that is public domain (such as Row, Row, Row Your Boat). Either write the music out or hum or play it into a recorder so you won't forget it.
Create lyrics that center around an idea and fit your melody. Keep the lyrics simple and easy to memorize. Try to include humor.
Write a copy of your song (lyrics and music) or record it.
Perform the song for children or for small groups and ask for feedback. They can be your most helpful critics. Ask questions and observe whether they seem to be enjoying the song and whether they're able to catch on easily and sing along.
Analyze popular children's songs to see what elements make them noteworthy. Begin by analyzing the lyrics of "Twinkle, Twinkle Little Star." Lines one, two, five and six rhyme. Lines three and four rhyme. The subject matter (stars) is simple and pertains to something that intrigues and amazes children.
Consider the melody and rhythm of "Twinkle, Twinkle Little Star." The range only contains six notes, which makes it simple. Another element of simplicity is the repetition of melodic patterns. The beginning and ending phrases are the same, and the two phrases in the middle copy each other as well. The song is written in standard 4/4 time. The steady beat is apparent and easy to sing or tap out.
Consider the melody and rhythm of "Old MacDonald Had a Farm" next. The melodic range is narrow (five notes) and the rhythm is simple, which makes it easy to sing. The song is written in a major key, which makes it sound happy.
Evaluate the lyrics of "Old MacDonald Had a Farm." The subject matter is about a farm and its animals. The animal sounds are easy and fun for children to imitate.