I start with the seven vowel phonemes that the letters of the alphabet can be divided into. I encourage students to try and guess the sounds first.
I elicit a word that has the sound in it and write this above each phoneme to help students remember the sound.
Then I get the students to work out which sounds are short and which are long. For the long sounds I ask them what the symbols have in common, in order to teach them as early as possible that symbols with two dots and two symbols together (diphthongs) are long sounds.
We start putting the letters of the alphabet in columns underneath the phonemes as a class and then students work alone or in pairs to complete. Check together by reading down each column. This also helps you to spot which letters of the alphabet cause your students problems.
The following lesson I usually revise the seven phonemes by preparing a song gapfill where the gaps are words that have the same sounds. We quickly revise the phonemes, writing an example word for each. Then I dictate the words needed to complete the song and students individually write them under the corresponding sound. They check together and we go over any problem words. Then we listen to the song and they complete the worksheet. For pre-intermediate and intermediate students I've used Stand By Me (Ben E. King) and for intermediate and upper intermediate students I've used New York (U2) and I'm With You (Avril Lavigne).