Have Fun Teaching

It happens that to teach the ABC, I sometimes use the Have Fun Teaching Channel in You Tube:

https://www.youtube.com/user/havefunteaching?feature=watch

Those are very simple songs, with nothing else than to teach one letter at the time. The songs are dynamic and will keep your young students awake, you may let them dance !

About teaching ABC to children, it is good for them at first to be able to say, or to sing, the alphabet from A to Z, but you will notice that if you show letters randomly, children won't recognize them.
My advice is then that after your children are able to recite the alphabet, you teach them vowels one by one, until your children or students remember the 5 vowels: A, E, I, O, U.

Once your kids know the vowels, you can go on the letters ending with the 'ee' sound: B (Bee), C (See), D (Dee)... Then you, and your children, will be able to write simple words with the vowels they learned at first.

Once these two steps completed, teach to your students other letters: F, H, J...

Do this, each time trying to write or read easy words, until the children are able to recognize all the letters of the alphabet randomly.

you can use a deck of 'ABC' cards, and put aside the letters you show to students each time that they don't remember what letter it is, and at the end insisting only on the letters that are the most difficult to remember.