In terms of cardio for fat loss, high intensity interval training seems to be the generally accepted way to go. In contrast to steady state cardio (such as running for 30 minutes at a steady pace), you work in timed bursts of effort. To explain more clearly, an example would be to cycle at an easy level on a stationary bicycle for two minutes, then increase the level and cycle hard for one minute. This is what I do for my NROLFW HIIT!
After reading up on reddit, fitness blogs, etc, it looks like there are many types of HIIT – most differences are in the time split. I think 2min/1min works for me. It gives me enough time to recover and catch my breath before going hardout again. A couple of years ago, Tabata training seemed to be a big thing. Its basically a four minute workout, which sounds time-efficient, but in reality it’s the effort of one workout compressed into a short time period. You work hard for 20 seconds and then rest for ten. I would not recommend it to someone new to fitness who doesn’t particularly like cardio. I absolutely hated it. I was super unfit, and it just highlighted how much I sucked.
Currently, on my 2min easy/1 min hard program I only cycle for a total of 15 minutes. And I do it after I lift, and only once or twice a week. I really enjoy it. This is something I’d keep doing after I finish the program.