It's difficult to reach your goals if you don't set a plan and track against it. There are three ways to track your fitness level.
1. The way you feel - understand your body and how you feel compared to less active times in your life. As your fitness level increases so will your energy and mental alertness.
2. The way you look - if you have high expectations, this method may not be the best choice. You may reach a high level of fitness, but still not have the body image you were hoping to see. Understand that this takes time. Be patient and enjoy the other physical changes like increased energy and sense of well being.
3. Logging your fitness routine - a tried and true method that's only getting easier with technological innovations. Track your goals and progress using a training monitor and training log.