A piece of advice, for free:
Don't try putting an onion somewhere new. Just put the onions in the same place every time, so that you don't forget about them until they gradually liquify and mysteriously fill your home with a faint, untraceable odor, that, when finally exposed directly to the organs of sense, results in an hour of retching and cleansing and sorrow. Onions go in the onion place, every time!