Many young students remember information the best when it is presented in the form of a story. These lesson plans for digraphs take advantage of this fact by teaching students about digraphs through "letter stories."
As the teacher, you can give each of the vowels their own personalities. For example, the letter "e" might be very excited, and the letter "a" might be very angry. To teach students what "ea" says, you can write the digraph on the board and then tell a story about excited "e" and angry "a." For example, perhaps "a" chases "e" all around the classroom because she is so upset at him, and "e" treats it as a joke, laughing like this: "Hee ee ee!" all around the room. Let children act it out to engage more kinesthetic learners. Repeat this type of instruction for each vowel digraph you teach.
This method of instruction is much more effective than the typical "when two vowels go walking, the first one does the talking" rule, since that rule is disproved for so many words, such as "chief" and "cause." Using this method, you can eventually expand on the stories to include the exceptions. For example, if you have taught "ea" using the above story, you can expand the story to include the "e" coughing with exhaustion at the end, saying "eh, eh, eh." This would explain why sometimes "ea" makes the short "e" sound, as in "head."