When it comes to New Year's Resolutions, or setting any goal for that matter, remember to be realistic. Rather than telling yourself that you're going to go from not exercising at all to working out for 3 hours a day, 7 days a week; work up to that. Start with a half hour 3 times a week and build on that.
Trouble sticking to your New Year's Resolutions? Be sure to choose a resolution that is meaningful to you; something that you really want to accomplish, rather than something that your family or society tells you to do.
Most sources say it takes 3-4 weeks to break a habit. Keep this in mind when trying to change eating, health or exercise habits. Pick a date 3 weeks to a month down the road that you want to have the habit completely changed by, then gradually work toward this: gradually increase your exercise, gradually decrease the number of cigarettes etc.
Schedule your workouts ahead of time in your daily-planner like you would a meeting or appointment. Try writing the day and time of your workouts a few weeks in advance, and if you need to cancel one, reschedule it right away!
Even when you're "too tired", get out there and exercise. Exercising helps to energize us, so chances are you'll feel better afterwards.
Having trouble keeping weight off? Find out the reasons behind your overeating; do you eat when you're stressed, bored, lonely, depressed etc.? Identifying these triggers and learning to deal with them without food will greatly serve long term weight control.
Setting goals is an important part of working out and exercising. If you don't know why you're doing what you're doing, there's a pretty good chance you're wasting a lot of your efforts and not seeing maximum results.
Whether you are trying to lose weight or gain it, trying to eat healthier or exercise more, tracking is extremely beneficial. Keep track of how much you've lost/gained/eaten/exercised, whatever it is that motivates you. This will also give you an idea of the habits and exercises that help you to or keep you from achieving your goals.
Having trouble sticking with your cardio routine? Pick an activity you enjoy doing. Playing basketball or swimming at increased intensity a couple times a week is just as beneficial as going for a jog.
While going for a walk, try tuning into an audio book rather than listening to music. Especially if it's a suspenseful story you might catch yourself exercising longer and looking forward to your next walk, and the next chapter.