http://bazaarboom567hsuxjspmwurpl7lyx23p7r2byg22vwfhv5yubvvezid.onion/faq/for-vendors/dead-drops-guide
In short: Be careful and play fair You need to: Pack an item well so that a cargo doesn't get wet in the rain or snow, even if it stays there for a long time. Choose the right location, somewhere is not too crowded, but not completely secluded either.