Should you keep track of your heart rate
Tracking your heart rate helps you in cardio working out effectively: it tells you when the challenge is too easy (heart rate under 130), how many calories you burnt and also gives you a good hint in progress (heart rate lower then at the beginning after doing the same exercise for some weeks). There will be people telling you to work out in a specific range to burn more fat. I personally don't agree to this: as long as you are young and healthy, higher is better. Makes you fitter and the overall calories burnt are higher which helps you losing weight.