If I just want a quick ride, a favourite short loop is to ride along the Calder Valley Cycleway to Mytholmroyd (to avoid the busy A646), ascend 'the longest continuous gradient in England' ...
... turn left at Blackstone Edge reservoir and do a very rapid 1.75 mile descent on the A58, then bear left onto a network of lovely undulating hilltop lanes, leading to a rapid descent back to Mytholmroyd, and return home on the Cycleway. 18.3 miles with about 1,600 ft of climbing, some fine views, and fun descents. Not too much traffic if busy times are avoided.
Doing routes the other way round is often a good way of extending your 'repertiore' but I don't like that one in reverse because I'd be climbing for 1.75 miles on the busy A58. Vehicles would be overtaking going about 50 mph faster than me, whereas descending it, I almost keep up with the cars.
When planning routes, I look for quiet roads, challenging hills and good scenery. Sometimes, it is necessary to use busy roads, but I prefer to keep them to a minimum.
I have about 4 or 5 favourite local routes, most of which are also good reversed so I'd say that I have about 8 routes that I use over and over again, ranging from the one above to ones that are about 3 times the distance with 3 times the climbing.