How to get started?
When I do release outdoors, I always put the book in a Release Bag from the Supply Store to protect it.
I suspect that books left on the bus may get thrown away when the bus is cleaned.
I leave nearly all of mine outside, in bags - on benches, in or propped against trees, on walls, or when indoors sometimes in museums or galleries. Bear in mind that you won't hear back from most of them, and make sure they're well labelled.
I do quite a bit of posting books to other members too - you will find forums for bookboxes and rays, and for random acts of kindness.