You work on phonetic or phonemic awareness, so the children learn to connect particular sounds with the appropriate letters of the alphabet.
You can start working on sight words -- the words that are so commonly used in English that we know them by sight, don't have to sound them out every single time. This is especially worked on in first grade, but it's helpful if it's begun in Kindergarten.
Make games and songs out of these tasks. There are umpteen ways to do this.