Get some magnetic letters and teach your baby a letter each week.  You can start at the beginning and choose the letter a.  Introduce the letters as capital and lowercase, so your child knows the difference.  Then spend a moment each day creating words that start with the letter a.  When you begin this, you should start with words that have the short a sound.  You can show your baby words like ant, apple, ax, etc...  Once you have shown your baby the letter a and words, move on to a new letter.  Your baby will naturally learn phonics in this manner, without formal lessons.