1. Make REALISTIC goals. If you want to lose weight set a goal, for example, to lose 10 pounds in 2 months. It may seem small, but when you accomplish it in less than 2 months you will likely be more proud of your accomplishment than setting a goal to lose 30 pounds in 3o days and you don't meet it.
2. Make PROGRESSIVE goals. Start low then build up to your ultimate goal. If by the end of 2010 you want to run a half marathon set little goals within that bigger goal. Start with running a 5k (3.1 miles) by Spring, then a 10k (6.2 miles) by Summer/ Fall, then finally end the year with a half marathon (13.1 miles) by late Fall/Winter. Use the same concept for strength training. If you are out of shape, or have not lifted weights ever/ in a long time, start slow. Start with lighter weights and build your endurance/strength up properly. Remember to work all major muscle groups including your shoulders/ neck, arms, back, abdominals, quadriceps, hamstrings, and lower leg muscles to have an adequate strength balance. Try a rotation between upper body and lower body muscles. On even days (Monday, Wednesday, Friday) work only upper body and then on odd days (Tuesday, Thursday, Saturday) work only lower body muscles. This concept helps let your muscles rest, heal, build, and rejuvenate properly. By having progressive goals it will help you avoid injuries and not feel defeated from the start.
3. EXERCISE and DIET are like 2 peas in a pod. To lose weight you can't just change your exercise routine or just your diet. You have to change both. Start making healthy changes to your diet. Drink less soda. Eat less sugar. Choose wheat over white. Try adding fruits, veggies, and/or nuts to your diet as a snack instead of chips or sweets. Choosing better alternatives are key.
4. DON'T QUIT when it gets hard or you are not seeing results as fast as you want. Stick to it. Your hard work will pay off in the end. Make exercise part of your routine. It's going to take a few months for it to feel "normal" that you want to exercise. Set a certain part of your day aside for exercise and dedicate that time 5-7 days a week to only exercise. Plan other tasks and obligations around that time frame. That way you can't use lack of time as a main excuse to not be active. You can use the time before work/school, your lunch break, or the time after work/school as your exercise time. Fit it into your routine and forget all the excuses to not exercise and be active.
It is going to be hard at first, but just remember exercising and losing weight will start to feel natural as long as you stick to it! You will start to feel better all around. So go out and start exercising, and start motivating others around you to do the same!