Consistently checking your RHR.. The lower it is the better, but not too low, it might causes heart attack. about 4x are good.. Fitness level can be train through a lot of type of exercises, as long you have good diets and exercise 3times a week you're consider a fit person already.

@TS, thanks for the thread! It's really motivating me to run more. haha, planning for my first run for KL 10K hosted by Nike.