For many years I was responsible for planning leisure rides for my previous club. We had a good library of past routes but I took it upon myself to plan new ones. In those days we not only published the route online but also produced a printed route-sheet which was handed out to participants at the start of the ride, as not all members used the internet, or had access to printers, or Garmins etc. (nowadays the club just publishes the RWGPS map and link). I used an OS map, and then checked out the route on Street View, and if possible cycled the route and took notes of junction priorities, dangerous locations and so on, so as to inform the route-sheet.
Nowadays I still don't use a Garmin, I check out a new route before riding, on OS maps, bike-hike, Street View, map my ride, RWGPS etc. and carry an A4 printed map of the area I'm riding in to refer to if necessary. For me it's all part of the enjoyment of cycling.
I'm constantly surprised by the Garmin-equipped I ride with who often appear to have little knowledge of the area we're riding through other than the route programmed.