it depends on the climate where you live , if your from the northern us or canada the digging season is pretty much over by now and i won't be digging again till the spring .
but if your looking for older bottles its best to check older properties like farms , along old roads and parks/docks that have been in the same location for years
all of the above and with the rivers try to find spots where they curve or have obstructions that can trap bottles. As storms come and go old bottles break loose and can be found just laying on the bottom of those areas. I have a few spots where I can check one day and find a couple and go back a few weeks latter and a few more wash up. For some reason under bridges seem to trap a lot of bottles. not just because people throw them off bridges most of them wash further down river. but under the bridge and imeadate area seem to trap some.I have about 5 crates full of bottles from 1870's to the 50's just from the nearby rivers. Good luck and welcome.