Figuring Out my Workout

A couple of years ago I bought a Nordictrack elliptical 12.7.  I've been been using it about five days a week lately.  Recently I've been trying to figure out the best way to use it.  I feel there must be a way to get the best workout out of it.  I am not sure if I should try to get as many steps as my fitbit can record? Should I keep my heart rate high for as much of the workout as I can? should I try to burn as many calories as I can according to my fitbit?

I can set the resistance and the incline of the steps.  There are also a large number of reset workouts.  I've tried a couple different workout ideas.  I change them up when I get board.  I just don't know what would actually get the best workout for my time.

My current workout is getting as many steps as I can for 20 minutes while listening to music.  I start with a log ramp setting and low resistance, moving them up one notch with each song. When my legs start to get tired and I cannot keep a good pace, I switch to high ramp setting, high resistance, and pump hard at that slower pace.  Every minute or so I reduce the ramp setting or resistance. 

I am not sure if this is the right way to build up my work out capacity or not.  I want to be able to work out longer and harder.  I want to use my 40 minutes or so more effectively.  I want to be able to keep up a good pace for a longer time.  I need to track my actions better to figure out all these things.