Anyone of these can work as long as it can be measured and accomplished. Ferguson recommends starting with a smaller, achievable goal and working your way up. Gradually increase the frequency or intensity, or both, at your own pace, month by month or week by week. Don't start all out because that's a sure way to burn out. When thinking of a fitness goal, you should keep in mind what kind of exercise you want to do.
Some people consider cross-training to avoid the monotony of a single activity.
Athletes use this approach, and I think it's helpful in personal fitness, too. Select a menu of things you can do for a long time so that you don't get tired of doing only one of them. Setting a personal fitness goal, however, does not just include physical fitness. Physical and nutritional fitness are closely related. Being physically fit requires energy to exercise and taking in good food will help give you that.