Students of a certain age can use 3-D blocks and other shapes to create buildings. To make the activity more thought-provoking, after they have finished building the structure, you can ask them to determine the floor area, perimeter, and volume of the building. In addition, you can require the student to build specific structures using only certain specific shapes.
For younger children, using clay is another hands-on activity to encourage thinking about 3-D shapes. The children can form different shapes using the clay and notice that they are three-dimensional. They can count the sides and corners of each shape.
Students can use toothpicks and peas (or the like) to construct 3-D shapes. The peas should be the corners connecting the toothpicks. This activity is both hands-on and gives a great visual of the shapes, specifically their lines, angles and corners. Students can choose which shapes to make or can be instructed to create specific ones.
Another activity for students is to examine the "real world" for 3-D shapes. Either working independently or with a partner, students can create lists of objects in the world and the shapes they are composed of. This can be made more challenging by instructing the student to find the shape within the shape. For example, a house is a square and a triangle, but what are smaller shapes within these two larger ones?