Consonants produce sounds that are more consistent and easier to identify than vowels. Therefore, they make a good starting point for learning to read.
Initially, work should be done on identifying beginning consonant sounds (ex: t-t-t tulip).
After that, activities can focus on identifying final consonant sounds (ex: cat ends with the t-t-t sound)
When children learn to recognize the sounds of consonants at the beginning and end positions of words, they gain the ability to look at a word and make a reasonable guess as to what it might be. Viewing the word in the context of a picture will help reinforce this skill.