Introduce one letter at a time, and reinforce it before you move on to the next letter. Say the letter sound, and hold up pictures of objects starting with that sound (bed, boy, box, bear). Let the children draw the letter shape in a variety of ways: on paper, in sand, with strips of playdough, and even in chocolate pudding.
Send children on a search for items starting with each letter. You can hide things at home or in the classroom, play a game of "I Spy," or go on a walk in the yard or playground, looking at balls, bats, birds and bushes.
Serve food starting with a specific letter---it's guaranteed to be one of the most popular ABC activities. For "b," slice up bananas, bake bread, heat up beans, eat berries or buy bon bons.
Reinforce the ABCs through reading, and online games and lessons. You'll find fun letter sounds and illustrations on websites such as StarFall.com, and you can learn how to form letters on abcLearningTime.com. Entertaining books include "SuperHero ABC" by Bob Mcleod (HarperCollins, 2008); "Eric Carle's ABC" (Grosset & Dunlap, 2007); and the classic "Dr. Seuss's ABC: An Amazing Alphabet Book!" (HarperCollins, 1996).
Songs and rhymes are a great way to learn the alphabet. Ron Brown's "What's That Sound?" is a lively way to teach short vowel sounds; Jack Hartmann's "Move to the Alphabet" lets kids form the shape and height of the letters with their bodies. You can find a variety of songs on websites including SongsForTeaching.com.