Taking your measurements regularly can help give you an idea of your progress.
Tracking your weight loss is always a good way to track progress. Keep in mind though that sometimes you may find you are gaining more muscle and not losing weight, but your measurements may be getting better.
Keep a journal of your workout, food intake, weight, measurements and whatever else you want to keep track of.
Learning about your BMI and watching that improve is always helpful to tracking your fitness.
An activity tracker can help keep you motivated to hit your step goals. You can also get one that helps track your sleep, water intake and so much more.
Cardio stamina is a great way to help track fitness levels. For example, how fast you can run a mile or how long you can run without stopping, as time progresses track how you improve.