Here are 25 tips from someone who has been on both sides.

1. The first thing to do is to ask yourself: Why are you exercising? Are you trying to get in shape for an upcoming event? Do you want to lose weight, sleep better, increase your energy, gain strength, add muscle tone and flexibility, or just feel a heightened sense of well being? If the reason you are exercising has anything to do with someone else (for example, your boyfriend says you need to lose weight or get in shape), you need a new reason (and, quite possibly, a new boyfriend).

2. Set goals. Set both a short term goal, to achieve in three to six weeks, and a long term goal, to achieve over the course of a year. Make sure your goals are achievable enough that they are not discouraging, but high enough that you have an incentive to tie your workout shoes each day. It is also important that your goals are specific and directly related to your specific motivation for exercising. For example, my main motivation for exercising is to consistently maintain my brighter mood and the calm, energized feeling that I get only from exercising, so my goal is to work out at least 5 days per week. My other motivation is to gain strength and cardiovascular endurance, so my other goals have to do with how long and how quickly I run.

3. Keep an exercise journal or log. Write down how your exercise is making you feel each day. How is your exercise benefiting your mood, energy levels, quality of sleep, weight, and so on? Do some exercises have more significant effects than others? Chart your progress in regard to your specific goals.

4. Take photos of yourself each month in your workout gear so you have a visual record of your results.

5. Make sure you are working out hard enough to release endorphins. Of course, you will want to talk to a doctor before starting any workout regimen, and you want to make sure that you are exercising at the optimum level for you, your body type, and your fitness level. I find that I am much more likely to continue with an exercise program if each workout releases those endorphins and immediately improves they way I feel.

6. Advertisements for fitness products (especially athletic shoes) can be tremendously motivating. Purchase a fitness magazine and make an inspirational collage of images, advertisements and slogans that speak to you. Post your collage where you will see it each day.

7. Make sure you are using proper technique. You want to avoid injury, above all, so check with a doctor or trainer if you experience any pain, or if you are not sure whether you are doing a particular exercise correctly.

8. Join an online community, such as WeightWatchers.com or Ediets.com, which encourages you to log and track your exercise each day.

9. If you enjoy working out with someone, call a friend to help hold you accountable for those daily workouts.

10. Join a group that combines fitness goals with charity fundraising. The Team In Training, from the Leukemia and Lymphoma Society, for example, provides training to walk or run a whole or half marathon, or to participate in a triathlon or 100 mile bike ride, all while raising money for a good cause.

11. If you prefer to work out alone, give yourself something fun to do while you exercise. Find some good heart pumping music or listen to books on tape. A suspenseful audiobook may be all you need to get on those running shoes each day.

12. Identify the excuses you like to use and have a ready made response. If time is an issue, make sure your workout clothes are ready to go. If you have young children, get a good jogging stroller or set up a babysitting swap with another mom in your neighborhood: you can watch her children while she works out and vice versa.

13. Make sure you have the right gear, which can make all the difference in the comfort level of your workout. A good pair of shoes is essential. And weather resistant clothing or a membership to an indoor gym can help you fight off your own excuses when weather conditions are less than ideal.

14. Once you find an exercise that you particularly enjoy, do a Google search to find out more about any coaches or specialists that may be able to provide inspiration or special training, either through tapes, books, or online resources. If you are a runner, for example, check out JohnBingham.com.

15. Recognize that your will to exercise is going to fluctuate, and exercise anyway. Sometimes it helps if I promise myself that I can stop my workout after 10 minutes if I still want to. At that point, I am usually feeling so much better that I finish the workout.

16. Place a giant star on your calendar each day to indicate that you completed your workout. These visual rewards can be so motivating.

17. Change your routine as you reach new goals. Add zest to your workout and avoid the exercise plateau by increasing the intensity or the duration of your workout, or by trying a new workout or sport.

18. Hire a trainer. If you are in an exercise rut, consider consulting with a personal trainer for a session or two. You will learn new techniques and find fresh motivation, as well.

19. Try not to take more than one day off at a time. I have found this really important to avoid losing valuable momentum. If I take two days off, it becomes very easy to take another day, and then another day. That means that if your workout is only part of your weekday routine, weave it into your weekend routine, too.

20. Be gentle with yourself. If you miss a workout or two or three, get right back to your regular schedule. You will feel better instantly.

21. Choose an exercise that you are likely to do each day. Some experts say that walking is the best exercise simply because it is something that is easy to do on a continual basis. There is no need for special equipment, and you can do it absolutely anywhere.

22. If you are walking or running, get a good pedometer to help you track your progress.

23. Schedule your daily exercise on your to do list and in your planner. Think of it as simply something you need to do before your head hits the pillow.

24. Give yourself simple rewards. It is generally best if these rewards are not edible, since a food reward can be a tad demoralizing after you have just worked to burn so many calories in a workout. For long term goals, treat yourself to a new pair of athletic shoes or other fitness equipment. For short term goals, consider a new fitness magazine, workout video, or simply fresh flowers for the dining room table.

25. Try to think of exercise as something you do for yourself: a gift you give yourself, a way to stay balanced and focused, and time when you can be alone with your thoughts.