I sometimes struggle with this. I can spin, not an issue, but usally end up with an average cadance of 85. Todays ride for example my highest cadance was 182 on a downhill but my average was 85. I find when riding with a big group that's moving fast I.E. 50km/h in a paceline sometimes it takes to much out of me to ride a fast cadance even on the short but steep climbs I find sometimes it's easier to use 1 gear to "hard" and push it rather than spin. Guess I fall into the whatever works catagory, my knees don't bother me so I must be doing something right.