Best cardio methods?

At our disposal we have a treadmill, excersise bike with pedals at the front, stepping machine and a cross trainer.



Me and my partner have two seperate goals:

Mine is to increase stamina, not wanting to comprimise size as I am a bulker.

My partner is trying to loose weight/ fat.





can somebody recommend me a good cardio routine? incoprating different methods i.e interval training. And please explain how do i do this? what heart rate suits us whilst training/ resting etc?



thanks