I am now thinking that the best way is to take the bottles to the pharmacy and they dispose of it professionally. But that would only work well for people who get their meds at a brick-and-mortar pharmacy - you drop off the old bottle for proper disposal and pick up a new bottle.

i get the medications in the mail, so for me it would be an extra trip... still, something to think about (maybe combined with grocery shopping). Also, the community mental health clinic I go to has a mailbox-like receptacle for disposing of old/unneeded medications. I guess it can be used for empty bottles, too.