Cut down on rest times
Doing a set of dumbbell curls and then sitting down on your butt for 2 minutes before repeating generally does nothing to improve cardio. It also eats away at precious time in the gym that could be spent on improving other areas of the body. Cutting the rest time down to 30 seconds or less will keep your heart rate elevated all while shortening the workout, allowing you more time to work on the areas you tend to neglect. You can even train more biceps with that time if you must.
