Spinning works. Although my average speed was 1 mph slower than before on the same trail for the same distance, I felt much better afterwards. My knees actually feel better after the ride than before. I stopped a little for pictures and walked the bike around a guy on wheelchair.
Anyway, I try to keep the cadence between 72-80 (90 passing) rpm, does that consider spinning cadence?
Also, bike shorts works. First time I put them on, my first thought was "damn, never know my butt and my manhood is so big"!
They increased my comfort immensely despite I got one of the cheapest one (Ascend Jetstream) on Nashbar.
I rode till there's little light (8:50pm) from above. Since I'm riding in a exercise bike path, I'm in no danger. However, a headlight probably will be my next purchase.
Still tweaking on position though. Moving the seat a little, the handlerbar angle, stem height, seat height, seat angle. Glad it's so many way to adjust, but frustrated for so many THINGS to adjust.
That is a decent all-day cadence. What you will pick up is the ability to spin more efficiently, i.e. you will pedal closer to a circle rather than squares. Over time you should see your hips rock less if they are currently and you will be able to comfortably attain a higher cadence. Of course proper setup will help you spin better.
When you can reasonably do 110-120 for short durations, consider yourself a good pedaler. Racing can get you up to 150 and higher. Of course these are extremes and terrain will dictate what cadence is appropriate for you. You are doing well at 70-90.
If you don't already have clipless pedals, consider getting them or at least toe clips.