Quickly make up a simple story of a short paragraph or find one in a book. For example: "Tony woke up and looked outside. The ground was covered in snow. He silently cheered while he left his room to find his mom. She gave him the news he was hoping for! School was closed for the day!"
Now ask the students to write things that the story didn't tell them directly, but that they figured out by inferring. Students should come up with things like Tony was a student in school, it was winter or Tony enjoys snow days.
Explain to students that making inferences is like looking for clues. You can even let them cut magnifying glasses out of a reproduced paper or card stock and hold them up, pretending to be detectives. Encourage them to find clues in a passage or story by being a good detective. Start by asking them to look for details that support the way the characters feel. For example, "She started to cry" lets us know as readers that the character is sad, without specifically saying that.
Show the students a short scene from a movie or television show without any sound. After it has ended, ask the children if they were able to follow any of the plot without hearing anything. For example, the facial expressions, body language and backgrounds will all help the children to draw conclusions. If time permits, let the students break into small groups to make their own silent skits and perform them for the class, so that they can have more turns drawing conclusions.
Show the students pictures cut from albums of families doing things together like going to the zoo or visiting the beach, and ask the students to write sentences drawing conclusions about how the people in the picture feel and what they are doing or getting ready to do. When they are done, let them share some of their writing and remind them that the pictures did not explicitly "tell" them anything, but that they were able to gather lots of information from them anyway.