Step1
Sing the words to the alphabet song over and over.
Step2
Teach the child to sing the song to the tune of "Twinkle, Twinkle, Little Star."
Step3
Repeat the song over and over. "A,B,C,D,E,F,G,
H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y and Z. Now I know my ABC's, next time won't you sing with me."
Step4
Expose the child to other people singing the song. Sometimes they need to hear it in a different voice.
Step5
Start off singing the song in a tempo slower than you normally would. This will help the child get the lyrics into his head. Once he starts singing with you begin speeding up the song until it is at normal tempo.
Step6
Practice over and over again until your child is comfortable singing the song on his own.