Play the "Alphabet Song" for the toddlers approximately twice each day. Sing along with the song and encourage them to do the same.
Keep playing the song and singing along until each toddler can sing the song by himself with no help from anyone else.
Purchase an alphabet border -- with both uppercase and lowercase letters -- and put it on the wall within arm's reach. Play the "Alphabet Song" and point to each letter -- lowercase and uppercase -- as you sing it. Repeat twice a day while encouraging the toddlers to watch you point to the letters and sing along.
Plan activities for each day focusing on one letter. For example, spray shaving cream onto a table top and help toddlers to trace an uppercase and lowercase "A" into the shaving cream with their index fingers. Or give each toddler a sheet with an uppercase and lowercase letter on it, along with some common objects to color such as "apple" or "ant."
Hang a magnetic board on a wall in reach of the toddler and place a full set of magnetic letters on the board for toddlers to manipulate. They can push the letters around on the board while studying their shapes and saying each letter's name.
Show toddlers how to form the letters of the alphabet with their bodies. Stand in front of the toddlers and call out a letter. Position your body into a form that represents the letter or help several toddlers work together to position themselves to form a letter.