I lost 30 lbs. last year and still have 20 to go. Here's a few things I have learned along the way:
1. You need to be honest with yourself. Take a look at your eating habits and identify your weaknesses or triggers. Are you a night time snacker, do you graze all day, is portion control your issue, do you drink regular soda, etc? What can you cut out that will save calories.
2. It's simple math. In order to lose weight, you have to take in less than you burn. So, you either need to cut back on the calories you take in or increase your exercise or both. Being aware of the number of calories you eat will show you where to cut back and how to make better choices. I started my diet at 1200-1300 calories per day. When I hit 1300, I stopped eating. A couple days of hitting that before 4:00 p.m. really makes you plan and make better choices!

What worked for me was to plan my day in the morning and input what I planned to eat for the day (I used eDiets but you can also use free online calorie trackers like sparkpeople.com). That way, I could see what was high in calories and adjust before I ate something instead of after.
3. Increase your water intake. I drink about 80 oz. of water per day.
I'm sure there will be lots of other good advice. Good luck!