Fix Your Cardio Workout at home

Treadmill 

The Mistake - too much bouncing
The Fix - do a few leg swings to loosen the hips before you start
The Mistake - too many long steady runs
The Fix - add in intervals, vary 30 sec intensity with 1 min easy run repeat several times,  vary the length of interval and intensity.

Stationary Bike

The Mistake - seat too high or too low
The Fix - your leg should be fully extended at the lowest point of the pedal rotation
The Mistake - steady state rather than a quick pace
The Fix - vary intensity with 2- 3 minute intervals followed by a moderate cadence - repeat for 15-20 mins - stand on occasion to add variety of muscles worked.

Elliptical Trainer

The Mistake - too little resistance
The Fix - set resistance so you feel yourself pushing down the ramp
The Mistake - getting bored
The fix - try adding 90 sec interval blasts with recoveries twice as long over 20 minutes

Check out Women's Health for fixes on the rowing machine and stair stepper too

http://www.womenshealthmag.com/weight-loss/the-best-cardio-workouts