There are a few light and empty places you can be. Inside your mother is the first. After that there is the water; the bath, the lake, the river, the sea, the ocean, etc (even running your hands under the faucet while doing dishes does the trick). An airplane is an option, but not a very good one. You can also go into space, but that is not for many. You can jump off of things but that I would not recommend as it can become dangerous. You can hold your breath when you run, which will most likely result in some bruises and confusion, but I would definitely say its well worth it.
Personally for me, the closest I will ever come to hollow bones is a trampoline. Jumping is something you can do to float for just a split second, and live with the rush of falling with the wind forced up your nose, expanding your lungs to full capacity, then again floating upwards so very slowly . . .
Julia floats. She floats because that is what she knows to do. Jim floats because that is what he studied, this is his profession. They float together in a metal tube in the sky, over the planet, because of compulsion and unrest. Julia has long hair, which she has kept as such since she was a child, which spirals out of control around her head in whirls and fancies for months while Jim breaths ever so slowly to conserve his energy.