One effective way to practice this skill is to incorporate a daily cross checking activity into the class routine. Throughout the day children read the sentences and guess what the missing words could be. Before going home, we listen to all the guesses and figure out if they are reasonable guesses or not and why. I reveal one letter and we can eliminate some of the possibilities. I continue in this manner until the entire word is revealed.
Children use the context as well as the length of the covered word, to make predictions.
As the letters are exposed one at a time, students learn to look beyond just the first letter, as first graders often neglect to do.