Using a workout and food diary and a food scale are two tools that can help you achieve your body-shape goals.
A workout and food diary helps you honestly understand how consistently you are working out, and with what level of effort. Using a heart rate monitor will help you gauge and record your calorie burn during whatever exercise program you choose. I often use it to challenge myself during a particular class to measure when I burn more calories. I then mark what the type of exercise I performed and how I was feeling if that applies. I can also use my diary for seeing my strength progress over a period of months.