One of the keys to making cadence work for you is consistency. On a level run, start pedaling with at whatever cadence and gear setting feels comfortable. That will be your beginning cadence. As you start encountering hills maintain that cadence by shifting to whatever gear is necessary to maintain that cadence. After you do that for a few rides, try to spin just a little faster for the entire ride, but keep it consistent. You will gradually increase this cadence ride after ride. I see a lot of people who say that your cadence should be 90-100, well yes it probably should, but if your natural starting cadence is 50, then you cannot and should not try to maintain 100 your first ride out, anymore than you should try to do 25 mph your first ride out. Your goal is to keep a constant cadence. The terrain and wind will determine what your speed is going to be. Once you have done this for a few thousand miles, then you start working on some interval training or other techniques to start tweaking the speed up even more.