The answer to both questions may very well be hill running.
Running up inclines greatly increases the amount of muscular effort and energy your body uses, compared to running on typical flat surfaces. Basically, running up hills is a very intense form of whole-body cardiovascular exercise that will wear you out and "kick your butt" in a very short amount of time.
Hill running is the ultimate in short, intense, fat-burning exercise!
So go find a hill near your home... preferably one that's not too steep since you don't want to make it too difficult when you first start off. Then spend about 4 or 5 minutes warming up, either jogging in place, jumping rope, or walking up and down the hill at a brisk pace.
After you're thoroughly warmed up, perform intervals by running -- or, if you can, sprinting -- up the hill and then jogging or briskly walking back down again. Do this at least 5-7 times. Each week try to add at least one interval to the workout.
Of course, if you don't have access to hills -- or you just want to be "boring" -- you can always jump on a treadmill and set a 5% incline to simulate hill running.
Why Hill Sprints Are The Fastest Way Of Getting Strong, Fast, And Lean