The basic idea of putting things in alphabetical order is categorization. Students must first learn the alphabet and then how to put the words in the correct order. Cut out words from similar categories (such as animals, colors or nouns) and have students work together to place the words in alphabetical order. Students can sit in groups and race to see who can put the words in order the fastest.
Challenge your students by having them alphabetize themselves. Ask your students to stand up and get in alphabetical order by first name. Then, challenge them to get in order from last name. More advanced students can be asked to categorize themselves by alphabetical order by the color of their clothing (if more than one child is wearing the same color, have them default to first name).
If students are too young to spell, but are beginning to recognize words and what letter words begin with, ask them to alphabetize the objects in pictures. Choose pictures of objects that start with different sounds and ask students to challenge themselves to put them in order on the chalkboard or desk. Students can race two at a time in front of the classroom to make it even more interesting.
Websites such as MrsPerkins.com and English For Everyone offer free worksheets to help your students learn to alphabetize. Make it a game by having students race to finish first or organize students into groups of three or four and have them race the other groups to be the first to fill out the sheet accurately.