Decide what your fitness goals are and make a plan for achieving them (e.g. I want to jog three miles without stopping; I want to be able to do 10 pushups). You are much more likely to achieve your goals if you actually write them down somewhere, and share them with friends or family.

Be sure to set reasonable goals. If you've never exercised much until now, it's not realistic to expect that you'll start exercising every day for an hour. Start with 30 minutes of moderate exercise a few times a week, letting your body recover for a day between exercise sessions. Then, as you get fit, you can add more time and/or more days to your routine. If you're already fit but want to train more, write down your current schedule and see where you can reasonably add more time or days to your workout routine.

It is important to plan ahead for dealing with potential obstacles to your exercise plan. For example, if your parents suddenly ask you to help with something around the house during your exercise time, when and where will you make it up? If you will need assistance getting somewhere or buying equipment for your workouts, make those arrangements in advance. Remember that missing one day or one exercise session won't ruin your training; just get back on schedule as soon as possible.