For beginning sorting, you can define the categories by which the students are to sort. You can begin with shapes of various colors and sizes made from colored paper. The students respond to your questions, indication whether or not a particular shape can be placed in a given group. In various turns, you can have them sort by color, size and shape, using appropriate attribute names. Once they are able to sort in this way easily, encourage them to say why a particular shape can or cannot be placed in a particular group.
Junk Box SortingGuide your students through exploring and sorting various types of math manipulatives. Ask them questions to help them observe how things are alike and different and sorting various items in different ways.
source: Mathematics Their Way, Mary Baratta-Lorton