The two most common resolutions are to quit smoking and to lose weight. Unfortunately most people stop there. They say they want to lose weight but they don't make a specific plan to make it happen and by February the idea of weight loss is a distant memory.
Make a specific goal. Instead of saying that you want to simply lose weight, make a specific goal of how much you want to lose by when. You can also break down the weight loss into weekly or monthly goals. I recommend one to two pounds per week for a realistic goal.
Create an actionable plan. Write down specific ways you will lose weight. What, where, and when will you do exercise? What will you do to change your diet? Create an online account to keep track of your food intake on fitday.com or sparkpeople.com.
Get creative. You will bored after a few days of "diet food" if you don't plan some excitement in the routine Get new recipes (my faves are cookinglight.com and eatbetteramerica.com) and plan your meals so you don't fall into unhealthy old routines of high calorie take-out.
Snack regularly. I am a big believer in "Eat light, eat often." Have a low glycemic snack of between 100-150 calories in between meals to bridge your hunger so you don't overeat at the next meal.
Stay active. Changing how you eat is only half the battle. Increasing how much you move is the other half. I love the Hit the Deck workout for an at-home, quick workout. Make sure you get your cardio in, too. Every day is best!