Hang up large padding items for large surface areas such as a ceiling or wall using a staple gun or hammer and nails. Possible sound-absorbing items include blankets or sheets. Note that the thicker the material, the more effective the material will be at absorbing sound and echoes.
Wipe out any remaining food debris from empty egg cartons made out of Styrofoam or cardboard. Fill the empty cartons with newspaper or cotton batting to increase sound absorption and secure the additional material with painter's or duct tape. Hang the cartons on the desired area with the interior of the egg cartons placed against the surface and attach them with a staple gun or hammer and nails.
Cut mattress egg crate foam pads to the desired size with a pair of heavy scissors. Note that you will need large push pins or a staple gun to secure the egg crate foam, as nails may cause the foam to rip, especially if you're hanging the material on ceilings or walls.