Use stencils to make flying bats from paper.
Construct your own stencil design by tracing half a head and wing along the fold of a piece of black paper bent in half. Needle through a knotted piece of fishing line and hang them from temporary, invisible 3M hooks on the ceiling. Witches, half moons, ghosts and mice all work as well. If hanging them from the ceiling isn't an option, use hidden pieces of painters tape to attach them to the wall or up the risers of a staircase.
For more inspiration, view our Halloween Decorating Ideas photo gallery.